Population momentum is the proportion between the size of a stable (unchanging) population to the total size of the initial population that experiences a drastic shift in fertility to replacement rate (2.1 children per woman). [1]Demographers refer to population momentum as the size of the resulting population-equivalent population relative to the current size of the population.

Momentum occurs because older cohorts differ in absolute size from those cohorts currently bearing children. This impacts the immediate birth and death rates in the population that determines the natural rate of growth. For the US National Library of Medicine, the US National Library of Medicine says it needs to have an absolute zero amount of natural growth.

1.) Fertility rates would need to be reduced to the replacement rate (the net reproduction rate should be 1). If the fertility rate remains higher then the population would continue to grow.

2.) Next, the mortality rate stops declining meaning that it remains constant.

3.) Lastly, the age structure has to adjust to the new rates of fertility and mortality. This last step takes the longest to complete. [2]

Implications of Population Momentum

Population momentum has implications for population policy for a number of reasons.

1. With respect to high-fertility countries in the developing world , a positive population momentum, meaning that the population is increasing, states that these countries will continue to grow rapidly and rapidly in fertility.

2. With respect to lowest-fertility countries in Europe , a negative population momentum implies that these countries may experience population decline even if they try to increase their rate of fertility to 2.1. For example, some Eastern European countries show a population shrinkage even if their birth rates are recovered. The way to population momentum can become negative if the fertility rate is under the replacement level for a long period of time.

3. Population momentum shows that replacement level fertility is a long-term concept rather than an indication of current population growth rates. Depending on the extant age structure, a fertility rate of two children per woman may correspond to short-term growth or decline.

Calculation

To calculate population momentum for population A, a theoretical population is constructed in which the birth rate for population Under such conditions, the population will eventually stabilize into a population with no year-to-year population. The population is calculated by dividing this population by the population. [3] Momentum, Ω, can be expressed as:

{\ displaystyle \ Omega = (be_ {o}) Q}

{\ displaystyle Q = {1 \ over rx} {R_ {o} -1 \ over R_ {o}}}

In the original equation, b is the crude birth rate. In the second equation, r is the growth rate, R o is the Net Reproduction Rate of the non-changing population while o is the life expectancy at birth and x is the unchanging population mean age at childbearing. Q is the total number of births per initial birth. [1]

Causes

Population momentum is typically caused by a shift in the country’s demographic transition . [4] When mortality rates drop, the young survive and the aging population live longer. Fertility rates remain high, the population size to grow. [5] According to population momentum, even if high fertility rates were reproduced, the population would continue to grow due to the pre-childbearing population entering into childbearing years. [4]

Countries with a population momentum

The following list are countries that maintain growth despite a fertility rate of 2.1. However, some of these countries also maintain growth because of immigration.

  • albania
  • australia
  • austria
  • belgium
  • Bosnia and Herzegovina
  • brazil
  • Canada
  • china
  • cyprus
  • denmark
  • finland
  • la France
  • greece
  • Iran
  • luxembourg
  • Netherlands
  • norway
  • Portugal
  • Republic of Macedonia
  • serbia
  • Slovakia
  • South Korea
  • spain
  • sweden
  • switzerland
  • taiwan
  • thailand
  • United Kingdom
  • United States

Effects of Population Momentum on the Environment

Forests, wetlands and mangroves cover two thirds of potential agricultural land; they all rely on water. These percentages vary by region and fall within the range of 23% to 89%. If these areas were to be conserved, the amount of land could be increased to 550 million ha. The rapid population growth during the next 30 years leaves. The constant demand for land resources and water can cause some areas that, in the future, will be difficult to overcome. These regions may be forced to begin with their resources. These regions include Western Asia, South Central Asia and Northern Africa. [6]There has been a recent drive to develop global control and oversee systems to study the overlying causes and impacts of both nationally and internationally. [6]

See also

  • Human overpopulation
  • Demography
  • List of population concern organizations
  • Population stabilization

References

  1. ^ Jump up to:b Kim, Young J .; Schoen, Robert (1997-08-01). „Population momentum expresses population aging“ . Demography . 34 (3): 421-427. doi : 10.2307 / 3038294 . ISSN  0070-3370 .
  2. Jump up^ Bongaarts, John (2009). „Human population growth and the demographic transition“ . Philosophical Transactions of the Royal B Society: Biological Sciences . 364 (1532): 2985-2990. doi : 10.1098 / rstb.2009.0137 . ISSN  0962-8436 . PMC  2781829  . PMID  19770150 .
  3. Jump up^ Preston, Heuveline, and Guillot (2001) Demography: Measuring and Modeling Population Processes, 165
  4. ^ Jump up to:b Blue, Laura; Espenshade, Thomas J. (2011). „Population Momentum Across the Demographic Transition“ . Population and Development Review . 37 (4): 721-747. ISSN  0098-7921 . PMC  3345894  . PMID  22319771 .
  5. Jump up^ Weeks, John Robert (2016). Population: an introduction to concepts and issues . Boston, MA: Cengage Learning. ISBN  9781305094505 . OCLC  884617656 .
  6. ^ Jump up to:b FISCHER, GUNTHER; HEILIG, GERHARD K (1997). „Population momentum and the demand on land and water resources“ (PDF) . 0-www.jstor.org.skyline.ucdenver.edu . The Royal Society . Retrieved 2017-03-29 .