Population growth

Population growth

Overview
Population growth is the change in a 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...

 over time, and can be quantified as the change in the number of individuals of any species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in a population using "per unit time" for measurement.
In biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, the term population growth is likely to refer to any known organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

, but this article deals mostly with the application of the term to human
Human
Humans are the only living species in the Homo genus...

 populations in demography
Demography
Demography is the statistical study of human population. 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...

.

In demography, population growth is used informally for the more specific term population growth rate (see below), and is often used to refer specifically to the growth of the human population of the world
World population
The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be  billion by the United States Census Bureau...

.

Simple models of population growth include the Malthusian Growth Model
Malthusian growth model
The Malthusian growth model, sometimes called the simple exponential growth model, is essentially exponential growth based on a constant rate of compound interest...

 and the logistic model
Logistic function
A logistic function or logistic curve is a common sigmoid curve, given its name in 1844 or 1845 by Pierre François Verhulst who studied it in relation to population growth. It can model the "S-shaped" curve of growth of some population P...

.

Population growth 1800-2011: from 1 billion to 7 billion estimated in 31.10.2011.
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Encyclopedia
Population growth is the change in a 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...

 over time, and can be quantified as the change in the number of individuals of any species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in a population using "per unit time" for measurement.
In biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, the term population growth is likely to refer to any known organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

, but this article deals mostly with the application of the term to human
Human
Humans are the only living species in the Homo genus...

 populations in demography
Demography
Demography is the statistical study of human population. 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...

.

In demography, population growth is used informally for the more specific term population growth rate (see below), and is often used to refer specifically to the growth of the human population of the world
World population
The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be  billion by the United States Census Bureau...

.

Simple models of population growth include the Malthusian Growth Model
Malthusian growth model
The Malthusian growth model, sometimes called the simple exponential growth model, is essentially exponential growth based on a constant rate of compound interest...

 and the logistic model
Logistic function
A logistic function or logistic curve is a common sigmoid curve, given its name in 1844 or 1845 by Pierre François Verhulst who studied it in relation to population growth. It can model the "S-shaped" curve of growth of some population P...

.

Population growth 1800-2011: from 1 billion to 7 billion estimated in 31.10.2011. During the year 2011 according to estimates:
Population
Year Billion
1800 1
1927 2
1960 3
1974 4
1987 5
1999 6
2011* 7
UNFPA
United Nations Population Fund
estimate 31.10.2011

  • 135 million people will be born
  • 57 million people will die and
  • 78 million people will increase the world population.

Determinants of Population growth


Population growth is determined by four factors, births(B), deaths(D), immigrants(I), and emigrants(E).
Using a formula expressed as

∆P≡(B-D)+(I-E)

In other words, the population growth of a period can be calculated in two parts, natural growth of population (B+D) and mechanical growth of population (I+E),in which Mechanical growth of population is mainly affected by social factors, e.g. the advanced economies are growing faster while the backward economies are growing slowly even with negative growth.

Population growth rate


In demographics and ecology
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

, population growth rate (PGR) is the rate at which the number of individuals in a population increases in a given time period as a fraction
Fraction (mathematics)
A fraction represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, we specify how many parts of a certain size there are, for example, one-half, five-eighths and three-quarters.A common or "vulgar" fraction, such as 1/2, 5/8, 3/4, etc., consists...

 of the initial population. Specifically, PGR ordinarily refers to the change in population over a unit time period, often expressed as a percentage
Percentage
In mathematics, a percentage is a way of expressing a number as a fraction of 100 . It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% is equal to 45/100, or 0.45.Percentages are used to express how large/small one quantity is, relative to another quantity...

 of the number of individuals in the population at the beginning of that period. This can be written as the formula:


The most common way to express population growth is as a percentage, not as a rate
Rate
In mathematics, a rate is a ratio between two measurements, often with different units. If the unit or quantity in respect of which something is changing is not specified, usually the rate is per unit time. However, a rate of change can be specified per unit time, or per unit of length or mass or...

. The change in population over a unit time period is expressed as a percentage of the population at the beginning of the time period. That is:


For small time periods and growth rates, the added population is the growth rate multiplied by the time period.

A positive growth ratio (or rate) indicates that the population is increasing, while a negative growth ratio indicates the population is decreasing. A growth ratio of zero indicates that there were the same number of people at the two times -- net difference between births, deaths a growth rate may be zero even when there are significant changes in the birth rates, death rates, immigration rates, and age distribution between the two times.

Equivalently, percent death rate = the average number of deaths in a year for every 100 people in the total population.

If the length of the time is taken smaller and smaller, the PGR approaches the logarithmic derivative
Logarithmic derivative
In mathematics, specifically in calculus and complex analysis, the logarithmic derivative of a function f is defined by the formulawhere f ′ is the derivative of f....

 of the population function P. If the population as a function of time is exponential
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...

, say P(t) = Ceat, the logarithmic derivative is a. Thus, the PGR approximates the exponent a for populations with exponential growth.

A related measure is the net reproduction rate
Net reproduction rate
The net reproduction rate is the average number of daughters that would be born to a female if she passed through her lifetime conforming to the age-specific fertility and mortality rates of a given year. This rate is similar to the gross reproduction rate but takes into account that some females...

. In the absence of migration, a net reproduction rate of more than one indicates that the population of women is increasing, while a net reproduction rate less than one (sub-replacement fertility
Sub-replacement fertility
Sub-replacement fertility is a total fertility rate that leads to each new generation being less populous than the previous one in a given area. In developed countries sub-replacement fertility is any rate below approximately 2.1 children born per woman, but the threshold can be as high as 3.4...

) indicates that the population of women is decreasing.

Excessive growth and decline


Main articles: 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 population decline
Population decline
Population decline can refer to the decline in population of any organism, but this article refers to population decline in humans. It is a term usually used to describe any great reduction in a human population...



Population exceeding the carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...

 of an area or environment is called 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...

. It may be caused by growth in population or by reduction in capacity. Spikes in human population can cause problems such as pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

 and traffic congestion
Traffic congestion
Traffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...

, these might be resolved or worsened by technological and economic changes. Conversely, such areas may be considered "underpopulated" if the population is not large enough to maintain an economic system
Economic system
An economic system is the combination of the various agencies, entities that provide the economic structure that defines the social community. These agencies are joined by lines of trade and exchange along which goods, money etc. are continuously flowing. An example of such a system for a closed...

 (see population decline
Population decline
Population decline can refer to the decline in population of any organism, but this article refers to population decline in humans. It is a term usually used to describe any great reduction in a human population...

). Between these two extremes sits the notion of the optimum population
Optimum population
The optimum population is the size of a population that is optimal. There are, however, various opinions on what "optimal" means in this usage, resulting in various end-targets for it, but estimations usually take ecological sustainability and carrying capacity more or less into account...

.

Human population growth rate


Globally, the growth rate
Rate
In mathematics, a rate is a ratio between two measurements, often with different units. If the unit or quantity in respect of which something is changing is not specified, usually the rate is per unit time. However, a rate of change can be specified per unit time, or per unit of length or mass or...

 of the human population
World population
The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be  billion by the United States Census Bureau...

 has been declining since peaking in 1962 and 1963 at 2.20% per annum. In 2009, the estimated annual growth rate was 1.1%. The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.915%, 0.812%, and 1.092% respectively The last one hundred years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity made possible by the Green Revolution
Green Revolution
Green Revolution refers to a series of research, development, and technology transfer initiatives, occurring between the 1940s and the late 1970s, that increased agriculture production around the world, beginning most markedly in the late 1960s....

.

The actual annual growth in the number of humans fell from its peak of 88.0 million in 1989, to a low of 73.9 million in 2003, after which it rose again to 75.2 million in 2006. Since then, annual growth has declined. In 2009, the human population increased by 74.6 million, which is projected to fall steadily to about 41 million per annum in 2050, at which time the population will have increased to about 9.2 billion. Each region of the globe has seen great reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

 and Sub-Saharan Africa
Sub-Saharan Africa
Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...

, and also in South Asia
South Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...

, Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

, and Latin America
Latin America
Latin America is a region of the Americas where Romance languages  – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

.

Some countries experience negative population growth
Population decline
Population decline can refer to the decline in population of any organism, but this article refers to population decline in humans. It is a term usually used to describe any great reduction in a human population...

, especially in Eastern Europe
Eastern Europe
Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...

 mainly due to low fertility rates, high death rates and emigration
Emigration
Emigration is the act of leaving one's country or region to settle in another. It is the same as immigration but from the perspective of the country of origin. Human movement before the establishment of political boundaries or within one state is termed migration. There are many reasons why people...

. In Southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...

, growth is slowing due to the high number of HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

-related deaths. Some Western Europe
Western Europe
Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...

 countries might also encounter negative population growth. Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

's population began decreasing in 2005.

Growth by country


Population in the world increased from 1990 to 2008 with 1,423 million and 27 % growth. As persons the increase was among highest 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...

 290 million 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...

 192 million. Population growth was among highest in Qatar
Qatar
Qatar , also known as the State of Qatar or locally Dawlat Qaṭar, is a sovereign Arab state, located in the Middle East, occupying the small Qatar Peninsula on the northeasterly coast of the much larger Arabian Peninsula. Its sole land border is with Saudi Arabia to the south, with the rest of its...

 174 % and United Arab Emirates
United Arab Emirates
The United Arab Emirates, abbreviated as the UAE, or shortened to "the Emirates", is a state situated in the southeast of the Arabian Peninsula in Western Asia on the Persian Gulf, bordering Oman, and Saudi Arabia, and sharing sea borders with Iraq, Kuwait, Bahrain, Qatar, and Iran.The UAE is a...

 140 %.
Rank Country Population (thousands)
2010
Population (thousands)
1990
Growth (%)
1990-2010
World 6,895,889 5,306,425 30.0%
1  Mainland China 1,341,335 1,145,195 17.1%
2  India 1,224,614 873,785 40.2%
3  United States 310,384 253,339 22.5%
4  Indonesia 239,871 184,346 30.1%
5  Brazil 194,946 149,650 30.3%
6  Pakistan 173,593 111,845 55.2%
7  Nigeria 158,423 97,552 62.4%
8  Bangladesh 148,692 105,256 41.3%
9  Russia 142,958 148,244 -3.6%
10  Japan 126,536 122,251 3.5%

See also

  • Baby boom
    Baby boom
    A baby boom is any period marked by a greatly increased birth rate. This demographic phenomenon is usually ascribed within certain geographical bounds and when the number of annual births exceeds 2 per 100 women...

  • Population bottleneck
    Population bottleneck
    A population bottleneck is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing....

  • Population decline
    Population decline
    Population decline can refer to the decline in population of any organism, but this article refers to population decline in humans. It is a term usually used to describe any great reduction in a human population...

  • Population pyramid
    Population pyramid
    A population pyramid, also called an age structure diagram, is a graphical illustration that shows the distribution of various age groups in a population , which forms the shape of a pyramid when the population is growing...

  • Carrying capacity
    Carrying capacity
    The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...

  • 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:...

  • Demographic momentum
    Demographic momentum
    Demographic momentum is the phenomenon of continued population increase despite reduced reproductive rates. Even in the face of extreme measures aimed at lowering reproductive rates, the population will continue to grow due to a large proportion of its population entering its reproductive years.For...

  • 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...

  • Density dependent inhibition
    Density dependent inhibition
    In population ecology, density-dependent inhibition describes a situation in which population growth is curtailed by crowding, predators and competition. In cell biology, it describes the reduction in cell division...

  • Exponential growth
    Exponential growth
    Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...

  • Compound annual growth rate
    Compound annual growth rate
    Compound annual growth rate is a business and investing specific term for the smoothed annualized gain of an investment over a given time period...

  • Doubling time
    Doubling time
    The doubling time is the period of time required for a quantity to double in size or value. It is applied to population growth, inflation, resource extraction, consumption of goods, compound interest, the volume of malignant tumours, and many other things which tend to grow over time...

  • Biological exponential growth
    Biological exponential growth
    Biological exponential growth is the exponential growth of biological organisms. When the resources availability is unlimited in the habitat, the population of an organism living in the habitat grows in an exponential or geometric fashion....

  • Family planning
    Family planning
    Family planning is the planning of when to have children, and the use of birth control and other techniques to implement such plans. Other techniques commonly used include sexuality education, prevention and management of sexually transmitted infections, pre-conception counseling and...

  • Fatal Misconception: The Struggle to Control World Population
    Fatal Misconception
    Fatal Misconception: The Struggle to Control World Population is a 2008 book by Matthew Connelly, an associate professor of history at Columbia University....

  • 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...

  • Green Revolution
    Green Revolution
    Green Revolution refers to a series of research, development, and technology transfer initiatives, occurring between the 1940s and the late 1970s, that increased agriculture production around the world, beginning most markedly in the late 1960s....

  • Natalism
    Natalism
    Natalism is a belief that promotes human reproduction. The term is taken from the Latin adjective form for "birth", natalis. Natalism promotes child-bearing and glorifies parenthood...

     and Antinatalism
    Antinatalism
    Antinatalism is a philosophical position that assigns a negative value to birth, standing in opposition to natalism. It has been advanced by figures such as Arthur Schopenhauer, Peter Wessel Zapffe, Heinrich Heine, Emil Cioran, Philipp Mainländer, Philip Larkin, Chris Korda, Matti Häyry, Thomas...

  • Optimum Population
    Optimum population
    The optimum population is the size of a population that is optimal. There are, however, various opinions on what "optimal" means in this usage, resulting in various end-targets for it, but estimations usually take ecological sustainability and carrying capacity more or less into account...

  • 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...

  • Urban sprawl
    Urban sprawl
    Urban sprawl, also known as suburban sprawl, is a multifaceted concept, which includes the spreading outwards of a city and its suburbs to its outskirts to low-density and auto-dependent development on rural land, high segregation of uses Urban sprawl, also known as suburban sprawl, is a...

  • Immigration
    Immigration
    Immigration is the act of foreigners passing or coming into a country for the purpose of permanent residence...

  • Immigration reduction
    Immigration reduction
    Immigration reduction refers to a movement in the United States that advocates a reduction in the amount of immigration allowed into the country. Steps advocated for reducing the numbers of immigrants include advocating stronger action to prevent illegal entry and illegal immigration, and...

  • Rank mobility index
  • World population
    World population
    The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be  billion by the United States Census Bureau...

  • World population estimates
    World population estimates
    A list of data for historical and projected human population of planet Earth from various sources is recorded here for reference...

  • Logistic function
    Logistic function
    A logistic function or logistic curve is a common sigmoid curve, given its name in 1844 or 1845 by Pierre François Verhulst who studied it in relation to population growth. It can model the "S-shaped" curve of growth of some population P...

     - concept related to logistic model
  • Ronald Fisher
    Ronald Fisher
    Sir Ronald Aylmer Fisher FRS was an English statistician, evolutionary biologist, eugenicist and geneticist. Among other things, Fisher is well known for his contributions to statistics by creating Fisher's exact test and Fisher's equation...

     - who referred to the population growth rate as the Malthusian Parameter
  • List of countries by fertility rate
  • List of countries by population growth rate

External links