Washington State just issued revised population estimates–and they upped their forecast for population growth from 2000 through 2010 by 110,000.  Just a year ago, the state was predicting that the state would add about 745,000 new residents over the decade, with just over half from net migration (more people moving into the state than out of it). But the new forcast predicts 855,000 new residents, with higher rates of in-migration as more people are attracted to the state by a strengthening economy.

What seems particularly interesting to me, though, is the way the population growth estimate has moved around over the past 7 years:

It’s not as if the estimate got better and better, homing in on the right number as the decade went on.  It’s far more random than that—perhaps a sign that forecasters recognized a little too late what the consequences of a recovering economy might be.

Now, this isn’t meant as a critique of Washington’s state demographers—just as a reminder that the future is really, really difficult to predict, even if it’s your job.  Which is one more reason to take all sorts of predictions—from population to market prices to resource availability—with an appropriately-sized dose of salt.