Brian Moot, age 9, of Lansing, Mich., for his question:
HOW MANY PEOPLE LIVE ON EARTH?
Most countries have more births than deaths, so their population increases unless a net loss results from migration. If persons leaving a country are more numerous then persons moving in, migration contributed to population decreases. If immigrants are more numerous than emigrants, migration contributes to population increases.
At the end of 1977, it was estimated that the world's population was 4.105 billion. This was an increase of about 86 million since 1976, or an increase of 2 percent. The total population of the world has been increasing steadily for many years, and scientists estimate that it will continue for many years to come.
It has been estimated that in 1650 the world had a population of about 500 million. It doubled from 1650 to 1850 and then it more than tripled since 1850.
During the past 300 years there has been a lot of movement of the population. The Americas and Oceania were occupied by Europeans and their descendants and there was a shift of Russians across Asia to the Pacific and a movement of Chinese to Manchuria. Even so, Asia has had relatively few emigrants and it now has about three fifths of the world's population just as it did in the mid 1600s.
Most populous country in the world today is China. About 855 million people call that land home. Next three in line are India, with a population of about 625 million; Russia, with about 260 million people, and the United States, with about 220 million.
The movement of the population has been from rural areas to the cities. in 1800, only five out of every 100 persons in the United States lived in places of 2,500 or more population. In 1970, 66 out of 100 persons lived in places of this size or larger. In 1800, 20 percent of the population of England and Wales lived in cities, while today that percentage is about 78.
Most countries take official counts of their population on a regular basis. The last census in the United States was taken in 1970, with another one scheduled for 1980. The first federal count was made in 1790 at which time it was determined that nearly 4 million people lived in the country. In less than 190 years, the population has increased to about 56 times as great as it had been when the first census was taken.
About 5 percent of the people in the United States were born in other countries. About 88 out of every 100 persons are white, and about 11 out of every 100 are black. One percent of the population is made up of Indians, Chinese, Japanese and other nonwhite groups.
If the rate of growth continues as it has in the past, the population of the United States will be about 229 million in 1980 and about 244 million in 1985.