A、Because the people there need more labor to support the family. B、Because the people there have the habit to have a big family

The United Nations published a report that was called "The State of World Population". It shows that the growth rate of world population will actually go down in the next ten years. The growth rate will fall from the present 18% to a rate of about 16% by the end of this century. But the report also points out that problems of food, health care, housing care, housing, jobs and schools will get worse unless we do something about the situation.
    Why is this? Although the total growth rate of the world population will decrease in some countries there will be a big rise in the population. More people will be born in Third World countries than in the richer Northern countries. So the population will grow faster in poor countries; and the problems in these countries will be very serious. This is because the family is more likely to survive if there are a lot of children to work for the members who become old or who cannot find work. A survey of the United Nations also shows that the growth rate is low where there is a higher level of income, better education, more health care and better living conditions. In this aspect, government plays an important role. So, the conclusion of the United Nations report is: "Look after the people and the population will look after itself."