What Are the Causes of Human Population Growth in U.S?

From 1940 to 1990, United States population growth was remarkably steady, increasing at the rate of about 25 million people each decade. But the ten-year span of the 1990s saw the rate shoot up to over 32 million.

Surprise Increase

The rapid increase in population during the 1990s came as a surprise to many, since it was generally believed that the population cycle had matured and that even a slight decline was inevitable.

Legal Immigration

Part of the record 1990s population increase can be traced to a legal immigration rate almost double that of previous decades.

Fertility Rates

While native-born American fertility rates were below replacement level, new immigrants brought with them 1950s U.S. Baby Boom era ideas about what family size should be.

Definition

The fertility rate is a number that expresses how many children the average woman will give birth to during her lifetime.

Birth Rates

The United States birth rate dwarfs that of other developed countries. Europe and Japan both hover around a 1.3 fertility rate. The American fertility rate has been as high as 3.0 but has pulled back, as we approach the end of the first decade of the 21st century, to just over 2.0.

References

• 20th Century U.S. Population Growth by Decade
• U.S. Birth Rates and Population Growth