Fertility rates

The total fertility rate in a specific year is defined as the total number of children that would be born to each woman if she were to live to the end of her child-bearing years and give birth to children in alignment with the prevailing age-specific fertility rates. It is calculated by totalling the age-specific fertility rates as defined over five-year intervals. Assuming no net migration and unchanged mortality, a total fertility rate of 2.1 children per woman ensures a broadly stable population. Together with mortality and migration, fertility is an element of population growth, reflecting both the causes and effects of economic and social developments. The reasons for the dramatic decline in birth rates during the past few decades include postponed family formation and child-bearing and a decrease in desired family sizes. This indicator is measured in children per woman.

特定年份的总和生育率（Total Fertility Rate）被定义为：若一名女性存活至其生育期结束，且按照当时通行的分年龄生育率生育子女，则每名女性累计生育的子女总数。其计算方式为对以五年为间隔的分年龄生育率进行求和。在假设无净移民且死亡率保持不变的前提下，每名女性总和生育率达到2.1时，可维持人口规模大体稳定。生育率与死亡率、移民共同构成人口增长的影响要素，同时反映经济与社会发展的成因与影响。近几十年来出生率大幅下降的原因包括家庭组建与生育行为的推迟，以及理想家庭规模的缩小。该指标以每名女性的生育子女数为计量单位。