Those Unpredictable People

Demographers had no sooner told us that the population growth of Los Angeles County had leveled off than the population started to zoom again. The county is now home to more than 8 million people, having gained 600,000 since the 1980 census. At that time, experts predicted that the population of Los Angeles wouldn’t reach 8 million until the next century. Less than six years later, events have proved them wrong.

Demography is a funny business. Demographers are good at taking a statistical snapshot of the world and describing it as it is. But when they make projections, they’re about as successful as economists, which is to say, not very successful. And for the same reason. Human affairs have too many variables and too many unpredictables to be a precise science. Small, unseen causes can have large effects. The future does not follow in a straight line from the past.

Demographers do have a slight advantage over economists in being able to make reasonably good short-term forecasts. The number of children who will start school next year can pretty well be inferred from birth records of five years before.

But long-term population trends are a stab in the dark. As a result, many forecasts don’t come true, and what does come true often was unexpected. Demographers failed to foresee some of the major population developments of recent decades, including the duration of the postwar baby boom, the rise of the Sun Belt, the growth of women in the labor force and the explosion in the number of people living alone.

Population growth in Los Angeles County slowed markedly in the 1970s. In the decade’s early years, the population actually declined. So experts said the boom was over. Los Angeles “can no longer expect the rapid growth that it enjoyed in the past,” a report from the Rand Corp. concluded in 1984.

What the experts hadn’t counted on were higher-than-average birthrates in the Latino and Asian populations. For the first time in its history, the population of Los Angeles is growing by “natural” increase--the excess of births over deaths--and not by migration from elsewhere in the country. The demographers accurately foresaw the migration factor, but they didn’t anticipate the high birthrates among ethnic minorities.

Demographic forecasts, of course, are not just cold statistical projections. They have major effects on public policy and the allocation of resources. On the basis of the recent population increases in Los Angeles, some experts are projecting continued increases here into the 1990s. Others aren’t so sure.

It is wise to view all of these pronouncements with skepticism. There is only one prediction about the future that is usually true: it will surprise you.