EXAMPLE 11 The old folks are coming

A writer in Science claimed in 1976 that “people over 65, now numbering 10 million, will number 30 million by the year 2000, and will constitute an unprecedented 25 percent of the population.” Sound the alarm: the elderly were going to triple in a quarter century to become a fourth of the population.

Let’s check the arithmetic. Thirty million is 25% of 120 million, because

So the writer’s numbers make sense only if the population in 2000 is 120 million. The U.S. population in 1975 was already 216 million. Something is wrong.

Thus alerted, we can check the Statistical Abstract of the United States to learn the truth. In 1975, there were 22.4 million people over age 65, not 10 million. That’s more than 10% of the total population. The estimate of 30 million by the year 2000 was only about 11% of the population of 281 million for that year. Looking back, we now know that people at least 65 years old were 12% of the total U.S. population. As people live longer, the numbers of the elderly are growing. But growth from 10% to 12% over 25 years is far slower than the Science writer claimed.