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Opinion: Some data have big outcomes

In some countries, population is shrinking; in others, a significant proportion of live births are to mothers between the ages of 15 and 19; in advanced industrial countries, the proportion of people over the age of 65 is an economic disaster.

I recently received the World Population Data Sheet from the Population Reference Bureau. It is a two-foot by three-foot chart, listing population data for more than 200 countries. Across the bottom of the chart are several highlights gleaned from the thousands of pieces of data on the sheet. All of the highlights have important implications, but they need elucidation in order to be fully understood. In the following brief space, I’ll attempt to explain the big effects of the data.

1. By 2050, 39 countries and territories are projected to have fewer people than they have today.

To understand the significance of this bit of data, it is important to understand the “population explosion.” For thousands of years, human beings inhabited the earth, but it was not until the early 19th century that world population totaled 1 billion people.

It took only about 100 years to add a second billion. Then, it took only 30 years to add a third billion (1960), 15 years to add a fourth billion (1975), and 12 years to add a fifth billion (1985). This “explosive” growth was spurred by the Industrial Revolution.

In the 1960’s, a book by Paul (and his uncredited wife, Anne) Ehrlich, “The Population Bomb,” brought the “disastrous” effects of rapid population growth to public attention. As we entered the 1990’s, the rate of population growth began to slow. Still, in 1998, world population stood at 6 billion. Twelve years later, it was 7 billion (2010). And it will be a projected 8 billion (at the end of this year). This is the “aftershock” of the population bomb.

Now, the intervals between additional billions begin to get slightly longer. Based on current projections, world population will be 9 billion in 2037 (15 years from now). Then, it will take 19 years to reach 10 billion.

Obviously, the world continues to grow rapidly, but the rate of growth is slowing because many countries (mainly those that benefited most from the industrial revolution) have either stabilized (zero population growth) or achieved negative population growth (population shrinking). These are the “39 countries and territories” that are mentioned in the highlight.

2. Mothers ages 15-19 account for 15 percent of all births in Africa, Latin America, and South America, but only 3 percent in Europe, 4 percent in North America, and 5 percent in Asia.

It has been shown conclusively that girls and young women who have the benefit of education tend to delay childbearing, and this has had the most dramatic effect in those countries that have advanced economies. In “poor” countries, a teen who gives birth risks becoming a baby-making machine. This contributes to a high birth rate, and — because of a global decrease in the death rate — rapid population growth.

This phenomenon is a major factor in the continued growth of the earth’s population. Demographers combine a number of factors to create the total fertility rate or TFR (the total number of children that each woman will bear). The break-even point is a TFR of 2.1. In other words, if the average number of births for all women in a country is 2.1, the population will eventually stop growing and stabilize.

The total fertility rate for the United States is 1.6, but we continue to grow because of the effects of past rapid growth, and we have a positive rate of immigration (+0.6). In some countries, the TFR has been so low that they will have fewer people in the near future. By 2020, every European country had a TFR that was substantially below 2.1. In Asia, both China (largely because of decades of a one-child policy in some of its provinces) and Japan (because of its economic development) have TFR’s of 1.3, and South Korea has a TFR of 0.8.

These countries benefit from higher levels of education, better health care and, consequently, longer life expectancy. However, this rapid reversal causes problems with a statistic that was once referred to as the “dependency ratio.” This meant that a significant proportion of the population was both above and below the age at which it was presumed that people would be gainfully employed.

3. At 17 percent, the share of people ages 65+ in the United States nearly equals the share who are younger than age 15 (18 percent).

The ages signify times when there is an assumption that most people will not be part of the work force. Obviously, we can all state many exceptions to this, but demographers look at data gleaned from millions of people. So, Statement 3 indicates that 35 percent of our population is not working (and not part of those classified as “idle” or “unemployed”). Those below the age of 15 (or usually higher) must be provided for by their parents, some other working adult, or a state agency. Those over 65 may depend heavily on Social Security, Medicare, pension funds, and even their working children. In many cases, none of these sources is sufficient.

In 1935 when the United States passed the Social Security Act, life expectancy for men was 59.4, and for women it was 63.3. Life expectancy (unlike life span) is an average based on the observed number of deaths in a population at each age of development. Therefore, when the SSA was passed it was not expected that most people would live past the age at which they would be eligible for benefits.

However, a male child born this year can — on average — expect to live 76.1 years, and a female child can expect to live nearly 81 years. With people living significantly longer, the proportion of the population that is economically dependent on the rest of society increases, and the burden of funding Social Security, pensions, and other financial instruments falls on a shrinking population with a workforce that is increasingly being replaced by automation, cybernation, and robotics.

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Jim Glynn is Professor Emeritus of Sociology. He may be contacted at


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