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...

, replacement migration is the migration

Human migration

Human migration is physical movement by humans from one area to another, sometimes over long distances or in large groups. Historically this movement was nomadic, often causing significant conflict with the indigenous population and their displacement or cultural assimilation. Only a few nomadic...

 needed for a region to achieve a particular objective (demographic, economic or social). Generally, studies using this concept have as an objective to avoid the decline of total population and the decline of the working-age population. Projections calculating migration replacement are primarily demographics and theoretical exercises and not forecasts or recommendations.

The concept of replacement migration may vary according to the study and depending on the context in which it applies. It may be a number of annual immigrants, a net migration, an additional number of immigrants compared to a reference scenario, etc.

Types of replacement migration

Replacement migration may take several forms because several scenarios of projections population can achieve the same aim. However, two forms predominate: minimal replacement migration and constant replacement migration.

Minimal replacement migration

Replacement migration is a minimum migration without surplus to achieve a chosen objective. This form of replacement migration may results in large fluctuations between periods. Its calculation will obviously depend on the chosen objective. For example, Marois (2008) calculates the gross number of immigrants needed to prevent total population decline in Quebec. The formula is then the following:

• R'(t) = Replacement Migration avoiding the decline of population in year t
• A(t) = retention rate of immigrants year t, defined by (1 - instantaneous departure rate)
• ∆P(t,t 1) = change in the total population in the time interval t, t+1

Constant replacement migration

The constant replacement migration does not fluctuate and remains the same throughout the projection. For example, it will be calculated with a projection providing a migration of X throughout the temporal horizon.

Results

The raw results of replacement migration are not necessarily comparable depending on the type of replacement migration used by the author. Nevertheless, major demographics conclusions are recurrent:

• The replacement migration reached impossible levels in practice to avoid aging the population, to maintain dependency ratio or influence significantly the age structure of a region.
• For regions with a relatively high fertility rate, replacement migration avoiding a decline in the total population or the working age is not excessively high. However, for regions with very low fertility rate, migration replacement is very high and unrealistic.
• The level of fertility is a much more important than the Immigration
  Immigration
  Immigration is the act of foreigners passing or coming into a country for the purpose of permanent residence...
  
   on aging and age structure.
• The principal effect of immigration is on population effective without substantially modifying the structure.

Examples of results

Replacement migration to prevent the total population decline (annual average):

• Germany
  Germany
  Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
  
  : 340 000 (net)
• Canada
  Canada
  Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
  
  : 76 000 (number of immigrants)
• United States
  United States
  The United States of America is a federal constitutional republic comprising fifty states and a federal district...
  
  : 130 000 (net)
• Europe
  Europe
  Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
  
  : 1 900 000 (net)
• 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...
  
  : 340 000 (net)
• Quebec
  Quebec
  Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
  
  : 40 000 (number of immigrants)
• Russia
  Russia
  Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
  
   500 000 (net)
• Slovenia
  Slovenia
  Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
  
  : 6 000 (additional immigrants relative to the reference)

Replacement migration to prevent the decline of population of working age (annual average)

• Germany: 490 000 (net)
• Canada: 165 000 (number of immigrants)
• United States: 360 000 (net)
• Europe: 3 230 000 (net)
• Japan 650 000 (net)
• Quebec: 70 000 (number of immigrants)
• Russia: 715 000 (net)
• Slovenia: 240 000 (additional immigrants relative to the reference)