As mentioned before, a sharp population growth in developing regions is caused by the situation when the birth rate is quite high and its decline was slow, while the death rate after the war dropped more remarkably than it was expected.
Of course, besides that, the effect of population momentum, also mentioned previously, that is accumulated base population from pre-war time to present is huge and is an important factor. However, whichever it may be, trends of the future world population can be said to depended on the degree of falling of the birth rate in developing regions from now on.
Therefore, it is necessary to consider the tendency of the past, in both the developing and developed regions, and future projected trends by using the total fertility rate as an index. Table 3, based on U.N. Population Prospects, shows the trend of total fertility rates in both developing and developed regions separately.
Total fertility rate is the sum of age-specific birth rates at the time and allows for the elimination of influence of age composition. This rate, if it remains constant for a long period of time, becomes an index of the average number of children each woman should have through her reproductive period.
By the way, for developing regions, the total fertility rate (TFR, abbreviation for total fertility rate is used from now on) was quite high (6.13) for the period of 1950 - 1955. However, after around 1970, it started to drop remarkably, and was 3.83 for the period of 1985 - 1990 and 3.48 for period of 1990 - 1995. On the other hand, for developed regions, it is noticeable that TFR dropped relatively sharply.
Because of the drop took place in both developing and developed regions, the world wide TFR dropped from the level 5 to 3. Among developing countries, the decline in TFR is so remarkable, particularly for East Asia (including China), South East Asia, Central America, and the Caribbean islands. However, for those countries such as Sub-Saharan countries in Africa, Middle Eastern countries, Pakistan and Afghanistan and the subcontinent of India, TFRs are still very high. Especially for Sub-Saharan countries in Africa, the
