Saint Paul Pioneer Press, Minn., Real World Economics Column.

Byline: Edward Lotterman

Jul. 16--Few factors can have a greater effect on an economy than demographic change. We have seen this in the United States, where the population more than doubled during my mother's life, and in Brazil, where it has nearly quadrupled during my own.

Now the United States and other industrialized nations face low birth rates and aging populations. Longer life spans will pose a huge challenge to the United States and other countries over the next few decades.

But demographics is an area where even well-educated people get tripped up by apparently simple concepts, such as life expectancy. That does not help in forming equitable and efficient public policy responses to rapidly growing or rapidly aging populations.

Consider the following simple and apparently illogical assertion: Most people live much longer than average.

That is true in poor countries, as well as here in the United States and other wealthy …