fertility

Meaning: In sociology and demography, fertility is the number of live births actually occurring in a population. Fertility rates fall as societies industrialize, urbanize, and lower child mortality. Women's education and paid work, access to contraception, and the rising cost of raising children also push the rate down. Where children contribute to farm work or old-age support, fertility stays high.

Equation: Crude birth rate = (live births ÷ mid-year population) × 1000, in births per 1000 people per year. The general fertility rate uses women of childbearing age (roughly 15 to 44) as the denominator. The total fertility rate is the average number of children a woman would bear in her lifetime if current age-specific rates held.

On the MCAT: Passages on the demographic transition show birth and death rates across stages. Death rates fall first, so the population grows rapidly. Birth rates fall later, so growth slows. Expect questions asking how women's education, urbanization, or a pension system would change fertility. Replacement level is about 2.1 children per woman. Below that, a population eventually shrinks unless immigration offsets it.

Common confusion: Fertility is not fecundity. Fecundity is the biological ability to have children, while fertility is the actual outcome. A woman who chooses to have no children can be fecund but has zero fertility. Also, the crude birth rate counts the whole population, including men and children, so it is a rougher measure than the general fertility rate.