Demography

Demography

Overview
Demography is the statistical study of human
Human
Humans are the only living species in the Homo genus...

 population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

. It can be a very general science that can be applied to any kind of dynamic human population, that is, one that changes over time or space (see population dynamics
Population dynamics
Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes...

). It encompasses the study of the size, structure and distribution of these populations, and spatial and/or temporal changes in them in response to birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...

, migration, aging  and death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

.

Demographic analysis
Demographic analysis
Demographic analysis includes the sets of methods that allow us to measure the dimensions and dynamics of populations. These methods have primarily been developed to study human populations, but are extended to a variety of areas where researchers want to know how populations of social actors can...

 can be applied to whole societies or to groups defined by criteria such as education
Education
Education in its broadest, general sense is the means through which the aims and habits of a group of people lives on from one generation to the next. Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts...

, nationality
Nationality
Nationality is membership of a nation or sovereign state, usually determined by their citizenship, but sometimes by ethnicity or place of residence, or based on their sense of national identity....

, religion
Religion
Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

 and ethnicity.
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Encyclopedia
Demography is the statistical study of human
Human
Humans are the only living species in the Homo genus...

 population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

. It can be a very general science that can be applied to any kind of dynamic human population, that is, one that changes over time or space (see population dynamics
Population dynamics
Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes...

). It encompasses the study of the size, structure and distribution of these populations, and spatial and/or temporal changes in them in response to birth
Birth
Birth is the act or process of bearing or bringing forth offspring. The offspring is brought forth from the mother. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world...

, migration, aging  and death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

.

Demographic analysis
Demographic analysis
Demographic analysis includes the sets of methods that allow us to measure the dimensions and dynamics of populations. These methods have primarily been developed to study human populations, but are extended to a variety of areas where researchers want to know how populations of social actors can...

 can be applied to whole societies or to groups defined by criteria such as education
Education
Education in its broadest, general sense is the means through which the aims and habits of a group of people lives on from one generation to the next. Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts...

, nationality
Nationality
Nationality is membership of a nation or sovereign state, usually determined by their citizenship, but sometimes by ethnicity or place of residence, or based on their sense of national identity....

, religion
Religion
Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

 and ethnicity. Institutionally, demography is usually considered a field of sociology
Sociology
Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...

, though there are a number of independent demography departments. Formal demography limits its object of study to the measurement of populations processes, while the more broad field of social demography population studies also analyze the relationships between economic, social, cultural and biological processes influencing a population.

The term demographics
Demographics
Demographics are the most recent statistical characteristics of a population. These types of data are used widely in sociology , public policy, and marketing. Commonly examined demographics include gender, race, age, disabilities, mobility, home ownership, employment status, and even location...

 refers to characteristics of a population.

Data and methods


There are two methods of data collection: direct and indirect. Direct data come from vital statistics registries that track all births and deaths as well as certain changes in legal status such as marriage, divorce, and migration (registration of place of residence). In developed countries with good registration systems (such as the United States and much of Europe), registry statistics are the best method for estimating the number of births and deaths.

A census
Census
A census is the procedure of systematically acquiring and recording information about the members of a given population. It is a regularly occurring and official count of a particular population. The term is used mostly in connection with national population and housing censuses; other common...

 is the other common direct method of collecting demographic data. A census is usually conducted by a national government and attempts to enumerate every person in a country. However, in contrast to vital statistics data, which are typically collected continuously and summarized on an annual basis, censuses typically occur only every 10 years or so, and thus are not usually the best source of data on births and deaths. Analyses are conducted after a census to estimate how much over or undercounting took place.

Censuses do more than just count people. They typically collect information about families or households, as well as about such individual characteristics as age, sex, marital status, literacy/education, employment status and occupation, and geographical location. They may also collect data on migration (or place of birth or of previous residence), language, religion, nationality (or ethnicity or race), and citizenship. In countries in which the vital registration system may be incomplete, the censuses are also used as a direct source of information about fertility and mortality; for example the censuses of the People's Republic of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

 gather information on births and deaths that occurred in the 18 months immediately preceding the census.

Indirect methods of collecting data are required in countries where full data are not available, such as is the case in much of the developing world. One of these techniques is the sister method, where survey researchers ask women how many of their sisters have died or had children and at what age. With these surveys, researchers can then indirectly estimate birth or death rates for the entire population. Other indirect methods include asking people about siblings, parents, and children.

There are a variety of demographic methods for modeling population processes. They include models of mortality (including the life table
Life table
In actuarial science, a life table is a table which shows, for each age, what the probability is that a person of that age will die before his or her next birthday...

, Gompertz models
Gompertz curve
A Gompertz curve or Gompertz function, named after Benjamin Gompertz, is a sigmoid function. It is a type of mathematical model for a time series, where growth is slowest at the start and end of a time period...

, hazards models
Proportional hazards models
Proportional hazards models are a class of survival models in statistics. Survival models relate the time that passes before some event occurs to one or more covariates that may be associated with that quantity. In a proportional hazards model, the unique effect of a unit increase in a covariate...

, Cox proportional hazards models
Proportional hazards models
Proportional hazards models are a class of survival models in statistics. Survival models relate the time that passes before some event occurs to one or more covariates that may be associated with that quantity. In a proportional hazards model, the unique effect of a unit increase in a covariate...

, multiple decrement life tables
Decrement table
Decrement tables, also called life table methods, are used to calculate the probability of certain events.-Birth control:Life table methods are often used to study birth control effectiveness...

, Brass relational logits), fertility
Fertility
Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

 (Hernes model, Coale
Ansley J. Coale
Ansley Johnson Coale , was one of America's foremost demographers. A native of Baltimore, Maryland, he earned his B.A. in 1939, his M.A. in 1941, and his Ph.D. in 1947, all at Princeton University...

-Trussell models, parity progression ratios
Parity progression ratios
Parity progression ratios refers to the number of offspring a female has borne. It is contrasted with gravidity, which refers to the number of pregnancies, regardless of outcome....

), marriage (Singulate Mean at Marriage, Page model), disability (Sullivan's method, multistate life tables), population projections (Lee Carter, the Leslie Matrix
Leslie matrix
In applied mathematics, the Leslie matrix is a discrete, age-structured model of population growth that is very popular in population ecology. It was invented by and named after Patrick H. Leslie...

), and population momentum
Population momentum
Population momentum refers to population growth at the national level which would occur even if levels of childbearing immediately declined to replacement level. For countries with above-replacement fertility , population momentum represents natural increase to the population...

 (Keyfitz).
  • The crude birth rate
    Birth rate
    Crude birth rate is the nativity or childbirths per 1,000 people per year . Another word used interchangeably with "birth rate" is "natality". When the crude birth rate is subtracted from the crude death rate, it reveals the rate of natural increase...

    , the annual number of live births per 1,000 people.
  • The general fertility rate, the annual number of live births per 1,000 women of childbearing age (often taken to be from 15 to 49 years old, but sometimes from 15 to 44).
  • age-specific fertility rates, the annual number of live births per 1,000 women in particular age groups (usually age 15-19, 20-24 etc.)
  • The crude death rate, the annual number of deaths per 1,000 people.
  • The infant mortality rate, the annual number of deaths of children less than 1 year old per 1,000 live births.
  • The expectation of life (or life expectancy
    Life expectancy
    Life expectancy is the expected number of years of life remaining at a given age. It is denoted by ex, which means the average number of subsequent years of life for someone now aged x, according to a particular mortality experience...

    ), the number of years which an individual at a given age could expect to live at present mortality levels.
  • The total fertility rate
    Total Fertility Rate
    The total fertility rate of a population is the average number of children that would be born to a woman over her lifetime if she were to experience the exact current age-specific fertility rates through her lifetime, and she...

    , the number of live births per woman completing her reproductive life, if her childbearing at each age reflected current age-specific fertility rates.
  • The replacement level fertility, the average number of children a woman must have in order to replace herself with a daughter in the next generation. For example the replacement level fertility in the US is 2.11. This means that 100 women will bear 211 children, 103 of which will be females. About 3% of the alive female infants are expected to decease before they bear children, thus producing 100 women in the next generation.
  • The gross reproduction rate
    Gross reproduction rate
    The gross reproduction rate is the average number of daughters that would be born to a woman if she survived at least to the age of 45 and conformed to the age-specific fertility rate of a given year...

    , the number of daughters who would be born to a woman completing her reproductive life at current age-specific fertility rates.
  • The net reproduction ratio is the expected number of daughters, per newborn prospective mother, who may or may not survive to and through the ages of childbearing.
  • A stable population, one that has had constant crude birth and death rates for such long time that the percentage of people in every age class remains constant, or equivalently, the population pyramid has an unchanging structure.
  • A stationary population, one that is both stable and unchanging in size (the difference between crude birth rate and crude death rate is zero).


A stable population does not necessarily remain fixed in size, it can be expanding or shrinking.

Note that the crude death rate as defined above and applied to a whole population can give a misleading impression. For example, the number of deaths per 1,000 people can be higher for developed nations than in less-developed countries, despite standards of health being better in developed countries. This is because developed countries have proportionally more older people, who are more likely to die in a given year, so that the overall mortality rate can be higher even if the mortality rate at any given age is lower. A more complete picture of mortality is given by a life table
Life table
In actuarial science, a life table is a table which shows, for each age, what the probability is that a person of that age will die before his or her next birthday...

 which summarises mortality separately at each age. A life table is necessary to give a good estimate of life expectancy.

The fertility rates can also give a misleading impression that a population is growing faster than it in fact is, because measurement of fertility rates only involves the reproductive rate of women, and does not adjust for the sex ratio. For example, if a population has a total fertility rate of 4.0 but the sex ratio is 66/34 (twice as many men as women), this population is actually growing at a slower natural increase rate than would a population having a fertility rate of 3.0 and a sex ratio of 50/50. This distortion is greatest in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 and Myanmar
Myanmar
Burma , officially the Republic of the Union of Myanmar , is a country in Southeast Asia. Burma is bordered by China on the northeast, Laos on the east, Thailand on the southeast, Bangladesh on the west, India on the northwest, the Bay of Bengal to the southwest, and the Andaman Sea on the south....

, and is present in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 as well.

Basic equation


Suppose that a country (or other entity) contains Populationt persons at time t.
What is the size of the population at time t + 1 ?


Natural increase from time t to t + 1:


Net migration from time t to t + 1:


This basic equation can also be applied to subpopulations. For example, the population size of ethnic groups or nationalities within a given society or country is subject to the same sources of change. However, when dealing with ethnic groups, "net migration" might have to be subdivided into physical migration and ethnic reidentification (assimilation
Cultural assimilation
Cultural assimilation is a socio-political response to demographic multi-ethnicity that supports or promotes the assimilation of ethnic minorities into the dominant culture. The term assimilation is often used with regard to immigrants and various ethnic groups who have settled in a new land. New...

). Individuals who change their ethnic self-labels or whose ethnic classification in government statistics changes over time may be thought of as migrating or moving from one population subcategory to another.

More generally, while the basic demographic equation holds true by definition, in practice the recording and counting of events (births, deaths, immigration, emigration) and the enumeration of the total population size are subject to error. So allowance needs to be made for error in the underlying statistics when any accounting of population size or change is made.

History



Demographic thoughts can be traced back to antiquity, and are present in many civilisations and cultures, like Ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...

, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 and China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

. In ancient Greece, this can be found in the writings of Herodotus
Herodotus
Herodotus was an ancient Greek historian who was born in Halicarnassus, Caria and lived in the 5th century BC . He has been called the "Father of History", and was the first historian known to collect his materials systematically, test their accuracy to a certain extent and arrange them in a...

, Thucidides, Hippocrates
Hippocrates
Hippocrates of Cos or Hippokrates of Kos was an ancient Greek physician of the Age of Pericles , and is considered one of the most outstanding figures in the history of medicine...

, Epicurus
Epicurus
Epicurus was an ancient Greek philosopher and the founder of the school of philosophy called Epicureanism.Only a few fragments and letters remain of Epicurus's 300 written works...

, Protagoras
Protagoras
Protagoras was a pre-Socratic Greek philosopher and is numbered as one of the sophists by Plato. In his dialogue Protagoras, Plato credits him with having invented the role of the professional sophist or teacher of virtue...

, Polus
Polus
Polus is the nickname Plato gave to an Ancient Greek Athenian philosophical figure who lived in the 5th century BCE. He was a pupil of the famous orator Gorgias, and teacher of rhetoric from the city of Acragas, Sicily....

, Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 and Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

. In Rome, writers and philosophers like Cicero
Cicero
Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...

, Seneca
Seneca
-People:*Lucius Annaeus Seneca, Seneca the Younger aka Seneca , son of Seneca the Elder, Roman philosopher and playwright, tutor and advisor of Nero*Seneca the Elder , Roman orator and writer...

, Pliny the elder
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

, Marcus Aurelius, Epictetus
Epictetus
Epictetus was a Greek sage and Stoic philosopher. He was born a slave at Hierapolis, Phrygia , and lived in Rome until banishment when he went to Nicopolis in northwestern Greece where he lived the rest of his life. His teachings were noted down and published by his pupil Arrian in his Discourses...

, Cato
Cato the Elder
Marcus Porcius Cato was a Roman statesman, commonly referred to as Censorius , Sapiens , Priscus , or Major, Cato the Elder, or Cato the Censor, to distinguish him from his great-grandson, Cato the Younger.He came of an ancient Plebeian family who all were noted for some...

 and Collumella also expressed important ideas on this ground.

In the Middle ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, Christian thinkers devoted much time in refuting the Classical ideas on demography. Important contributors to the field were William of Conches
William of Conches
William of Conches was a French scholastic philosopher who sought to expand the bounds of Christian humanism by studying secular works of the classics and fostering empirical science. He was a prominent member of the School of Chartres...

, Bartholomew of Lucca
Bartholomew of Lucca
Bartholomew of Lucca also known as Tolomeo da Lucca or Ptolemy da Lucca was a medieval Italian historian....

, William of Auvergne
William of Auvergne, Bishop of Paris
William of Auvergne was a French priest who served as Bishop of Paris from 1228 until his death in 1249. He is also known as Guillaume d'Auvergne, Guilielmus Alvernus, or William of Paris.-Life:...

, William of Pagula
William of Pagula
William of Pagula , also known as William Paull or William Poull, was a 14th-century English canon lawyer and theologian best known for his written works, particularly his manual for priests entitled the Oculus Sacerdotis...

, and Ibn Khaldun
Ibn Khaldun
Ibn Khaldūn or Ibn Khaldoun was an Arab Tunisian historiographer and historian who is often viewed as one of the forerunners of modern historiography, sociology and economics...

.

The Natural and Political Observations ... upon the Bills of Mortality (1662) of John Graunt
John Graunt
John Graunt was one of the first demographers, though by profession he was a haberdasher. Born in London, the eldest of seven or eight children of Henry and Mary Graunt. His father was a draper who had moved to London from Hampshire...

 contains a primitive form of life table. Mathematicians, such as Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...

, developed the life table as the basis for life insurance mathematics. Richard Price
Richard Price
Richard Price was a British moral philosopher and preacher in the tradition of English Dissenters, and a political pamphleteer, active in radical, republican, and liberal causes such as the American Revolution. He fostered connections between a large number of people, including writers of the...

 was credited with the first textbook on life contingencies published in 1771, followed later by Augustus de Morgan
Augustus De Morgan
Augustus De Morgan was a British mathematician and logician. He formulated De Morgan's laws and introduced the term mathematical induction, making its idea rigorous. The crater De Morgan on the Moon is named after him....

, ‘On the Application of Probabilities to Life Contingencies’ (1838).

At the end of the 18th century, Thomas Malthus
Thomas Malthus
The Reverend Thomas Robert Malthus FRS was an English scholar, influential in political economy and demography. Malthus popularized the economic theory of rent....

 concluded that, if unchecked, populations would be subject to exponential growth
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...

. He feared that population growth would tend to outstrip growth in food production, leading to ever-increasing famine and poverty (see Malthusian catastrophe
Malthusian catastrophe
A Malthusian catastrophe was originally foreseen to be a forced return to subsistence-level conditions once population growth had outpaced agricultural production...

). He is seen as the intellectual father of ideas of overpopulation
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...

 and the limits to growth. Later, more sophisticated and realistic models were presented by Benjamin Gompertz
Benjamin Gompertz
Benjamin Gompertz was a British self educated mathematician and actuary, who became a Fellow of the Royal Society...

 and Verhulst
Pierre François Verhulst
Pierre François Verhulst was a mathematician and a doctor in number theory from the University of Ghent in 1825...

.

The period 1860-1910 can be characterized as a period of transition wherein demography emerged from statistics as a separate field of interest. This period included a panoply of international ‘great demographers’ like Adolphe Quételet
Adolphe Quetelet
Lambert Adolphe Jacques Quetelet was a Belgian astronomer, mathematician, statistician and sociologist. He founded and directed the Brussels Observatory and was influential in introducing statistical methods to the social sciences...

 (1796–1874), William Farr
William Farr
William Farr was a nineteenth-century British epidemiologist, regarded as one of the founders of medical statistics.-Early life:He was born in Kenley, Shropshire, England to poor parents...

 (1807–1883), Louis-Adolphe Bertillon (1821–1883) and his son Jacques
Jacques Bertillon
Jacques Bertillon was a French statistician and demographer.Born in Paris, Bertillon was the son of statistician Louis Bertillon and the older brother of Alphonse Bertillon. He was educated as a physician but turned to statistical analysis. In 1880 he wrote La Statistique humaine en France...

 (1851–1922), Joseph Körösi (1844–1906), Anders Nicolas Kaier (1838–1919), Richard Böckh (1824–1907), Wilhelm Lexis
Wilhelm Lexis
Wilhelm Lexis was an eminent German statistician, economist, and social scientist and a founder of the interdisciplinary study of insurance....

 (1837–1914) and Luigi Bodio
Luigi Bodio
Luigi Bodio was an Italian economist and statistician, among the founders of Italian Statistics...

 (1840–1920) contributed to the development of demography and to the toolkit of methods and techniques of demographic analysis.

Transition


Contrary to Malthus' predictions and in line with his thoughts on moral restraint, natural population growth in most developed countries has diminished to close to zero, without being held in check by famine or lack of resources, as people in developed nations have shown a tendency to have fewer children. The fall in population growth has occurred despite large rises in life expectancy in these countries. This pattern of population growth, with slow (or no) growth in pre-industrial societies
Pre-industrial society
Pre-industrial society refers to specific social attributes and forms of political and cultural organization that were prevalent before the advent of the Industrial Revolution. It is followed by the industrial society....

, followed by fast growth as the society develops and industrializes, followed by slow growth again as it becomes more affluent, is known as the demographic transition
Demographic transition
The demographic transition model is the transition from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system. The theory is based on an interpretation of demographic history developed in 1929 by the American...

.

Similar trends are now becoming visible in ever more developing countries, so that far from spiraling out of control, world population growth is expected to slow markedly in this century, coming to an eventual standstill or even declining. The change is likely to be accompanied by major shifts in the proportion of world population in particular regions. The United Nations Population Division expects the absolute number of infants and toddlers in the world to begin to fall by 2015, and the number of children under 15 by 2025.

The figure in this section shows the latest (2004) UN projections of world population out to the year 2150 (red = high, orange = medium, green = low). The UN "medium" projection shows world population reaching an approximate equilibrium at 9 billion by 2075. Working independently, demographers at the International Institute for Applied Systems Analysis in Austria expect world population to peak at 9 billion by 2070. Throughout the 21st century, the average age of the population is likely to continue to rise.

Science of population


Populations can change through three processes: fertility, mortality, and migration. Fertility involves the number of children that women have and is to be contrasted with fecundity (a woman's childbearing potential). Mortality is the study of the causes, consequences, and measurement of processes affecting death to members of the population. Demographers most commonly study mortality using the Life Table
Life table
In actuarial science, a life table is a table which shows, for each age, what the probability is that a person of that age will die before his or her next birthday...

, a statistical device which provides information about the mortality conditions (most notably the life expectancy) in the population.

Migration refers to the movement of persons from an origin place to a destination place across some pre-defined, political boundary. Migration researchers do not designate movements 'migrations' unless they are somewhat permanent. Thus demographers do not consider tourists and travelers to be migrating. While demographers who study migration typically do so through census data on place of residence, indirect sources of data including tax forms and labor force surveys are also important.

Demography is today widely taught in many universities across the world, attracting students with initial training in social sciences, statistics or health studies. Being at the crossroads of several disciplines such as sociology
Sociology
Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...

, economics
Economics
Economics is the social science that analyzes the production, distribution, and consumption of goods and services. The term economics comes from the Ancient Greek from + , hence "rules of the house"...

, epidemiology
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

, geography
Geography
Geography is the science that studies the lands, features, inhabitants, and phenomena of Earth. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...

, anthropology
Anthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...

 and history
History
History is the discovery, collection, organization, and presentation of information about past events. History can also mean the period of time after writing was invented. Scholars who write about history are called historians...

, demography offers tools to approach a large range of population issues by combining a more technical quantitative approach that represents the core of the discipline with many other methods borrowed from social or other sciences. Demographic research is conducted in universities, in research institutes as well as in statistical departments and in several international agencies. Population institutions are part of the Cicred
Cicred
The Committee for International Cooperation in National Research in Demography, commonly known as CICRED, is a non-governmental organization accredited with the Economic and Social Council of the United Nations. Founded in 1972, it aims at developing cooperation amongst national population research...

 (International Committee for Coordination of Demographic Research) network while most individual scientists engaged in demographic research are members of the International Union for the Scientific Study of Population, or a national association such as the Population Association of America in the United States, or affiliates of the Federation of Canadian Demographers in Canada.

See also



  • Biodemography
    Biodemography
    Biodemography is the science dealing with the integration of biology and demography.Biodemography is a new branch of human demography concerned with understanding the complementary biological and demographic determinants of and interactions between the birth and death processes that shape...

  • Biodemography of human longevity
    Biodemography of human longevity
    Biodemography is a multidisciplinary approach, integrating biological knowledge with demographic research on human longevity and survival...

  • Demographic analysis
    Demographic analysis
    Demographic analysis includes the sets of methods that allow us to measure the dimensions and dynamics of populations. These methods have primarily been developed to study human populations, but are extended to a variety of areas where researchers want to know how populations of social actors can...

  • Demographic economics
    Demographic economics
    Demographic economics or population economics is the application of economics to demography, the study of human populations, including size, growth, density, distribution, and vital statistics.Analysis includes economic determinants and consequences of:...

  • Historical demography
    Historical demography
    Historical demography is the quantitative study of human population in the past. It is concerned both with the three basic components of population change--fertility, mortality, and migration--and with population characteristics related to those components, such as marriage, socioeconomic status,...

  • Linguistic demography
  • Nurgaliev's law
    Nurgaliev's law
    In population dynamics, Nurgaliev's law is an equation that describes the rate of change of the size of a population at a given time, in terms of the current population size...

  • Religious demography
  • Gompertz-Makeham law of mortality
    Gompertz-Makeham law of mortality
    The Gompertz–Makeham lawstates that the death rate is the sum of an age-independent component and an age-dependent component , which increases exponentially with age...

  • Medieval demography
    Medieval demography
    This article discusses human demography in Europe during the Middle Ages, including population trends and movements. Demographic changes helped to shape and define the Middle Ages...

  • National Security Study Memorandum 200
    National Security Study Memorandum 200
    National Security Study Memorandum 200: Implications of Worldwide Population Growth for U.S. Security and Overseas Interests was completed on December 10, 1974 by the United States National Security Council under the direction of Henry Kissinger....

     of 1974
  • Population
    Population
    A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

  • Population geography
    Population geography
    Population geography is a division of human geography. It is the study of the ways in which spatial variations in the distribution, composition, migration, and growth of populations are related to the nature of places. Population geography involves demography in a geographical perspective. It...

  • Population projection
    Population projection
    Population projection, in the field of demography, is an estimate of a future population. In contrast with intercensal estimates and censuses, which usually involve some sort of field data gathering, projections usually involve mathematical models based only on pre-existing data. A projection may...

  • Population reconstruction
    Population reconstruction
    Population reconstitution is a method used by historical demographers. Using records such as church registries the size and composition of families living in a given region in a given past time is determined...

  • Population statistics
    Population statistics
    Population statistics is the use of statistics to analyze characteristics or changes to a population. It is related to social demography and demography.Population statistics can analyze anything from global demographic changes to local small scale changes...

  • Replacement migration
    Replacement migration
    In demography, replacement migration is the migration needed for a region to achieve a particular objective . Generally, studies using this concept have as an objective to avoid the decline of total population and the decline of the working-age population...

  • Reproductive health
    Reproductive health
    Within the framework of the World Health Organization's definition of health as a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity, reproductive health, or sexual health/hygiene, addresses the reproductive processes, functions and system...


Social surveys:
  • Current Population Survey
    Current Population Survey
    The Current Population Survey is a statistical survey conducted by the United States Census Bureau for the Bureau of Labor Statistics . The BLS uses the data to provide a monthly report on the Employment Situation. This report provides estimates of the number of unemployed people in the United...

     (CPS)
  • Demographic and Health Surveys
    Demographic and Health Surveys
    The MEASURE Demographic and Health Surveys Project is responsible for collecting and disseminating accurate, nationally representative data on health and population in developing countries. The project is implemented by Macro International, Inc...

     (DHS)
  • European Social Survey
    European social survey
    The European Social Survey is a social scientific endeavour to map the attitudes, beliefs and behaviour patterns of the various populations in Europe.-History:The ESS was initiated by the European Science Foundation...

     (ESS)
  • Family and Fertility Surveys (FFS)
  • General Social Survey
    General Social Survey
    The General Social Survey is a sociological survey used to collect data on demographic characteristics and attitudes of residents of the United States. The survey is conducted face-to-face with an in-person interview by the National Opinion Research Center at the University of Chicago, of a...

     (GSS)
  • German General Social Survey
    German General Social Survey
    The German General Social Survey is a national data generation program in Germany, which is similar to the American General Social Survey ...

     (ALLBUS)
  • German Socio-Economic Panel (SOEP)
  • National Longitudinal Survey (NLS)
  • Panel Study of Income Dynamics
    Panel Study of Income Dynamics
    The Panel Study of Income Dynamics is the world’s longest running household panel survey. The PSID is a longitudinal panel survey of United States families that measures economic, social, and health factors over the life course and across generations...

     (PSID)
  • World Values Survey
    World Values Survey
    The World Values Survey is a global research project that explores people’s values and beliefs, how they change over time and what social and political impact they have. It is carried out by a worldwide network of social scientists who, since 1981, have conducted representative national surveys in...

     (WVS)

Organizations:
  • Office of Population Research
    Office of Population Research
    The Office of Population Research at Princeton University is the oldest population research center in the United States. It was founded in 1936....

     (Princeton University) (United States)
  • Population Reference Bureau
    Population Reference Bureau
    The Population Reference Bureau is a private, nonprofit organization which informs people around the world about population, health and the environment for research or academic purposes...

     (United States)
  • Population Studies Center at the University of Michigan
    Population Studies Center at the University of Michigan
    The Population Studies Center is one of the oldest demography centers in the United States, with a distinguished record in both domestic and international population research and training.- Introduction and Activities :...

     (United States)
  • International Institute for Applied Systems Analysis (IIASA) non-governmental research institution
  • Institut national d'études démographiques
    Institut national d'études démographiques
    The Institut national d'études démographiques is a French research institute specialized in demography and population studies in general.-A research institute founded in 1945:...

     (INED) (France)
  • Max Planck Institute for Demographic Research
    Max Planck Institute for Demographic Research
    The Max Planck Institute for Demographic Research is located in Rostock, Germany. It was founded in 1996 and moved into new buildings in Rostock in 2002. It is one of approximately 80 institutes of the Max Planck Society....

     (Germany)

Scientific journals:
  • Brazilian Journal of Population Studies
  • Cahiers québécois de démographie
    Cahiers québécois de démographie
    The Cahiers québécois de démographie is a peer-reviewed academic journal publishing original research in areas of demography, demographic analysis, and the demographics of Quebec and other populations....

    (Quebec Notebooks of Demography)


Further reading

  • Glad, John. 2008. Future Human Evolution: Eugenics in the Twenty-First Century. Hermitage Publishers, ISBN 1-55779-154-6
  • Gavrilova N.S., Gavrilov L.A. 2011. Ageing and Longevity: Mortality Laws and Mortality Forecasts for Ageing Populations [In Czech: Stárnutí a dlouhověkost: Zákony a prognózy úmrtnosti pro stárnoucí populace]. Demografie, 53(2): 109-128.
  • Preston, Samuel, Patrick Heuveline, and Michel Guillot. 2000. Demography: Measuring and Modeling Population Processes. Blackwell Publishing.
  • Gavrilov L.A., Gavrilova N.S. 2010. Demographic Consequences of Defeating Aging. Rejuvenation Research, 13(2-3): 329-334.
  • Paul R. Ehrlich
    Paul R. Ehrlich
    Paul Ralph Ehrlich is an American biologist and educator who is the Bing Professor of Population Studies in the department of Biological Sciences at Stanford University and president of Stanford's Center for Conservation Biology. By training he is an entomologist specializing in Lepidoptera , but...

     (1968), The Population Bomb
    The Population Bomb
    The Population Bomb was a best-selling book written by Paul R. Ehrlich and his wife, Anne Ehrlich , in 1968. It warned of the mass starvation of humans in the 1970s and 1980s due to overpopulation, as well as other major societal upheavals, and advocated immediate action to limit population growth...

    Controversial Neo-Malthusianist pamphlet
  • Leonid A. Gavrilov & Natalia S. Gavrilova (1991), The Biology of Life Span: A Quantitative Approach. New York: Harwood Academic Publisher, ISBN 3-7186-4983-7
  • Uhlenberg P.(Editor), (2009) International Handbook of the Demography of Aging, New York: Springer-Verlag, pp.113-131.
  • Paul Demeny and Geoffrey McNicoll (Eds.). 2003. The Encyclopedia of Population. New York, Macmillan Reference USA, vol.1, 32-37
  • Phillip Longman
    Phillip Longman
    Phillip Longman is an American demographer. Presently he is a Schwartz Senior Fellow at the New America Foundation, and he formerly worked as a senior writer and deputy assistant managing editor at U.S...

     (2004), The Empty Cradle: how falling birth rates threaten global prosperity and what to do about it
  • Joe McFalls (2007), Population: A Lively Introduction, Population Reference Bureau
    Population Reference Bureau
    The Population Reference Bureau is a private, nonprofit organization which informs people around the world about population, health and the environment for research or academic purposes...

  • Ben J. Wattenberg
    Ben J. Wattenberg
    Benjamin J. Wattenberg is an American conservative commentator and writer.-Early years:Wattenberg was born in The Bronx, New York, to Jewish parents, and went on to graduate from Hobart College in 1955, majoring in English. From 1955 to 1957 he was in the U.S. Air Force, based in San Antonio. He...

    (2004), How the New Demography of Depopulation Will Shape Our Future. Chicago: R. Dee, ISBN 1-56663-606-X

External links