Population Size

Population Size

The population size of a given nation or the world as a whole is affected by a variety of factors including birth , death , fertility , and migration rates . Thus , birth , or fertility , and death rates are interconnected in the following formula

Birth rate (b ? death rate (d rate of natural increase (r (Human Population Growth

In the US where 14 people are born per 1000 a year on average , and 8 people die for the same amount , the natural growth rate is 14-8 6 per thousand

Recently , most nations

experienced surges in natural growth rates triggered primarily by declines in death rates . These declines , in turn were caused by better nutrition , better health care , improved living standards , improved sanitation and immunization (Human Population Growth . Birth rates are typically lower in developed nations due to greater spread of family planning possibilities and cultural shifts , for instance , increase in the number of working women or greater focus on self-realization

Migration rate is another important factor defining the population size Thus , in a nation that experiences negative natural growth rate , the demographic situation can be corrected by influx of foreigners through migration . In the US , for instance , immigration is a major influence adding on average about 1 .1 million legal and 700 ,000 illegal immigrants to the population annually (CAIR , n .d . Besides , the situation is affected by the fact that new immigrants tend to have higher fertility rates so that by 2050 most population growth will be driven by post-1970 immigrants , while the pre-1970 population , is on track to peak at 247 million in 2030 and then gradually decline (CAIR n .d . Migration is attracted to regions that demonstrate high living standards and promise future economic development

In this way , birth , death , and migration rates all exert influence on population size . These influences can offset each other : for instance where birth rate falters , lower death rate can boost population growth Migration can also serve as an important factor in increasing population in places where natural growth has been slow

References

Colorado Alliance for Immigration Reform (CAIR (n .d . U .S . Population and Immigration Data , Projections and Graphs . Retrieved March 31 , 2006 from http /www .cairco .org /data /data_us .html

Human Population Growth . Retrieved March 31 , 2006 , from http /users .rcn .com /jkimball .ma .ultranet /BiologyPages /P /Populations .htm l

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POPULATION SIZE

31 March 2006...