RESUMO
PIP: The demographic explosion after World War II was due to the sudden drop in mortality rates without an equivalent decrease of birth rates. Most countries in Asia, Latin American and Africa have had a natural growth rate of approximately 2%/year, causing the population to double every 35 years. Fertility rates remained high due to local customs, socioeconomic environment, and religion; the mortality rate decreased dramatically due to medical progress and control of epidemics. The population in these less developed areas increased from 1950 to 1975 from 1.7 to almost 3 billion, and is equivalent to 83% of the world's total. The world's population increased from 2.5 to 4 billion. The U.N. estimates that the worldwide population growth rate will go down to 0.9% by the year 2025, primarily due to a decrease of the 2% growth rate in the less developed countries to 1.1%. According to UN projections, the worldwide fertility rate has decreased from 38/1000 in the 1950s to 28.9 in 1975-80; it will reach 17.6/1000 by the year 2025. The birth rate decreased by 50% in East Asia but only by 2.5% in Africa, where it is expected to remain at the 40-50 births per 1000 level, notably in countries such as Nigeria and Kenya. There has been a significant overall decrease in the world's mortality rate, and life expectancy rates increased from 45.8 in 1950 to 57.3 in 1980. The difference in life expectancy between the more developed and less developed regions was about 24.1 years in the 1950s and is now 17.3 years. Africa has the highest mortality rate and the lowest life expectancy (less than 50 years) as do India, Indonesia and Bangladesh. China, however, has had a 21-year life expectancy rate increase from 46 in the 1950s to 67. Worldwide, the infant mortality rate appears to be the decisive factor in the population growth rate having decreased 130/1000 in 1950-1955 to 88 in 1975-1980. In a LDC, the life expectancy of a newborn is 17 years less than that of a child born in a developed country; at age 5, its life expectancy is 8 or 9 years less. For those with a high standard of living in the developing world there is little difference with the developed world. In Brazil, for instance the low income groups in the Northeast have a life expectancy of 45 years and the more affluent groups in the South have a life expectancy of 67 years.^ieng