Patterns of fertility decline in developing countries, 1950-75.

Since 1965 there have been substantial declines in the crude birth rates of many countries in the developing world, particularly the largest countries. This auspicious trend is shown clearly in an analysis of population figures for the last 25 years, despite the fact that there are deficiencies in the data. In 1950 the average crude birth rate for developing countries was 42 per thousand per year. Over the next 15 years, declines in the crude birth rate were limited to a relatively few, and for the most part small, countries. After 1965, however, for the 13 developing countries with a population numbering 35 million and over, there have been declines in the crude birth rate averaging 13 percent, with declines of over 12 percent in 9 of them. The effects of a number of sociodemographic factors on crude birth rates are examined, and the analysis shows that increases in the age at marriage and decreases in marital fertility were the principal factors affecting declines since 1965.