For the three decades after WWII, incomes grew at about 3 percent a year for people up and down the income ladder, but since then most income growth has occurred among the top quintile. And among that group, most of the income growth has occurred among the top 5 percent. The pattern repeats itself all the way up. Most of the growth among the top 5 percent has been among the top 1 percent, and most of the growth among that group has been among the top one-tenth of one percent.

We're in a classic demand-shortfall recession. There aren't enough jobs because total spending is too low. Consumers won't lead the way because they're busy paying down debt and are fearful they'll lose their jobs, if they haven't already. Businesses, which are currently sitting on mountains of cash, won't spend either, because they already have sufficient capacity to produce more than people are willing to buy.

The fact that many private expenditures are mutually offsetting actually happens to constitute a remarkably good bit of fiscal news. Mutually offsetting spending patterns are wasteful in the same way that military arms races are. In such situations, if each party spends less, nothing is sacrificed, yet resources are freed up that can be put to much better uses.

One reason that might motivate a worker to accept a riskier job at higher pay, for example, would be that doing so would enable him to bid more effectively for a house in a better school district. But if other workers did likewise, none would achieve the goal they were striving for.

When people bump up against one another in the course of pursuing their goals, it is in everyone's interest to resolve any resulting problems in the least costly ways possible.

Many decry rising inequality because it makes those who've fallen behind feel impoverished. But it's done much more than cause hurt feelings. It has also raised the real cost to middle-income families of achieving many basic goals. The process begins with the completely unremarkable fact that top earners have been spending at a substantially higher rate than before. They've been building bigger mansions, staging more elaborate weddings and coming-of-age parties for their kids, buying more and better of everything.

Adam Smith's uncritically enthusiastic modern disciples portray his invisible hand theory as saying that market forces reliably harness selfish individuals to serve the common good. That's often true, but as Darwin recognized clearly, many traits that serve the interests of individual animals make life more difficult for larger groups.