The global and regional impact of mortality and fertility transitions, 1950-2000

摘要

During the second half of the twentieth century, the world population, and even more so the population of the less developed regions, experienced demographic changes at an unprecedented pace. According to United Nations (1999) estimates, the world's population was 2.521 billion in 1950 and it will be 6.055 billion in mid-2000. This represents a mean annualized growth rate of 1.75 percent per year; the corresponding figure for less developed regions is 2.09 percent per year. The reasons for this unprecedented world population increase are well known, but the numbers remain striking. Global average life expectancy at birth increased by 9.5 years in just 15 years (from 46.5 years in 1950-55 to 56.0 years in 1965-70), while the average life expectancy at birth gained 11.3 years in less developed regions (from 40.9 years to 52.2 years; United Nations 1999), almost certainly the fastest pace in human history (Durand 1967; Coale 1974). During the same period, world average fertility remained stable, as total fertility rates merely declined from 4.99 to 4.91. But in the following 30 years substantial fertility declines occurred in many parts of the world, and, where they did, the pace of the decline was again rapid. The average total fertility rate declined by half in less developed regions, from 6.01 births per woman in 1965-70 to 3.00 births per woman in 1995-2000 (United Nations 1999).