Populations
grow or decrease through the interplay of three factors: births, deaths, and migration.
Unlike other kinds of organisms, humans are also influenced by social, political, economic, ethical
factors.
Population change is calculated by subtracting
the number of people leaving a population (through death and emigration) from
the number entering it ( through birth and immigration) during a specified
period of time (usually a year):
Population
change = (Births + Immigration) – (Deaths + Emigration)
When
births plus immigration exceed deaths plus emigration, population increases;
when the reverse is true, population declines.
The
rate of the world’s annual population change (excluding migration) usually is
expressed as a percentage:
Birth rate – Death rate
Annual rate of
natural population change (%) = ------------------------- x 100
1,000 persons
Birth rate – Death rate
= -------------------------------
10
Social
Factors
The
major social factors that determine family size are the status and desirers of women in the culture. As women become better
educated and obtain higher paying jobs, they become financially independent and
can afford to marry later and consequently have fewer children. Better educated
women are also more likely to have access to and use birth control. What is
most important is the desire of women to limit the size of their families.
Political
Factors
Two
other factors that influence the population growth rate of a country are government policies on population growth
and immigration.
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