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9 Things You Should Know About Demography and Population Trends

Former Florida governor Jeb Bush was recently criticized for claiming that immigrants are more "fertile" than native-born Americans (he's mostly right). Bush's statement, along with debates about immigration reform and the latest news from the Census Bureau, have brought an issue that many people are confused about -- demography -- into the national spotlight. Here are 9 things you should know about demography and demographic trends.

1. Populations and subpopulations can change through three processes: fertility (the number of children that women have), mortality (the number of deaths that occur), and migration (the movement of persons from a locality of origin to a destination place across some pre-defined, political boundary). Demography is the statistical study of human populations and these changes.

2. Replacement level fertility is the level of fertility at which a population exactly replaces itself from one generation to the next. In developed countries, such as the United States, replacement level fertility can be taken as requiring an average of 2.1 children per woman. This means that 100 women will bear 211 children, 103 of which will be females. About 3% of the alive female infants are expected to die before they bear children, thus producing 100 women in the next generation. In countries with high infant and child mortality rates, however, the average number of births may need to be much higher.

3. Total fertility rate represents the number of children that would be born to a woman if she were to live to the end of her childbearing years and bear children in accordance with current age-specific fertility rates. From 2008-2012, the fertility rates for the countries with the highest population was: China (1.6); India (2.6); U.S. (1.9); Indonesia (2.1); Brazil (1.8).

4. Fertility rates began falling in Western, industrialized countries in 1968 (oral contraceptive, first introduced in 1960, had become widely used by then). By 1975, every Western First World nation was below the replacement rate. Over the course of the next two decades, massive fertility decline spread worldwide: In 1979, the global fertility rate was 6.0; today it's 2.52 and still declining.

5. Most population models suggest we are currently at "peak child," that is, the world currently has about 2 billion children and that number is likely to decline over time, not increase. Because of this, the world population will peak at 10 billion before declining.

6. In the U.S., the largest population group — whites who are not Hispanic — recorded more deaths than births last year for the first time ever. Between July 2011 and July 2012, an estimated 12,400 more white Americans died than were born. (The number of whites still increased slightly last year because immigration more than compensated for the gap between births and deaths.) Demographers have long expected that deaths among the non-Hispanic white population ultimately would outpace births, but they didn't expect it until the end of the decade.

7. Sub-replacement level fertility rates can have a wide-ranging effect on everything from marriage to sex trafficking to global conflict. For example, demographic projections suggest that by 2030 more than 25 percent of Chinese men in their late 30s will never have married. As demographer Nicholas Eberstadt points out, "The coming marriage squeeze will likely be even more acute in the Chinese countryside, since the poor, uneducated, and rural population will be more likely to lose out in the competition for brides. Beijing will have to determine how it will cope with a growing demographic of unmarried, underprivileged, and, quite possibly, deeply discontented young men."

8. Countries can sometimes offset low fertility rates by increasing immigration. According to Eberstadt, the U.S. population, according to U.S. Census Bureau projections, is set to grow by 20 percent, or over 60 million people (from 310 million to 374 million), between 2010 and 2030. By such projections, the population growth rate of the U.S. will nearly match India's. Virtually every age group in the country is set to increase in size over the next 20 years. Unlike all other affluent countries, the United States can expect a growing pool of working-age people (a moderate but steady rise averaging 0.5 percent per year over the next 20 years).

9. According to the World Bank, the nations with the largest proportions of unbelievers had an average annual population growth rate of just 0.7% in the period 1975-97, while the populations of the most religious countries grew three times as fast.

Recent posts in this series:

9 Things You Should Know About Fathers and Father's Day

9 Things You Should Know About Mothers and Mother's Day

9 Things You Should Know About Pornography and the Brain

9 Things You Should Know About Planned Parenthood

9 Things You Should Know About the Boston Marathon Bombing

9 Things You Should Know About Female Body Image Issues

9 Things You Should Know About the Gosnell Infanticide and Murder Trial

9 Things You Should Know About Edith Schaeffer

9 Things You Should Know About Duck Dynasty

Joe Carter is an editor for The Gospel Coalition and the co-author of How to Argue Like Jesus: Learning Persuasion from History's Greatest Communicator. You can follow him on Twitter.

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