The authors find that despite the popular notions about overconsumption, a typical family spends less on clothing today, discounted for inflation, than in the early 1970's. Similarly, it spends less on large appliances and on food, including going out to restaurants. As for vacation homes, the data suggest that 3.2 percent of families had them in 1973, and that 4 percent do now. Is this affluenza?

Rather, what families spend a lot more on, the authors calculate, is a house in a safe neighborhood with a good school -- about 70 percent more a year, discounted for inflation, for the typical family of four. The scarcity of good schooling has created a bidding war that drives up house prices in first-rate school districts.

And these families are not buying huge new homes. The average home size has been skewed upward by the wealthy. The typical family's house is, in fact, only a half room or so larger than it was 30 years ago.

The other factors driving spending are largely the costs of the two-income family. The authors find that typical payments for day care and preschool for two children can add enormously to the household budget.

Two workers also make a second car a necessity, and often a good second car.

Also, the cost of health insurance is often up, even when spouses work, because corporate benefit plans are demanding higher employee contributions. For the typical family of four, it is up by 60 percent.

And two incomes often mean a substantial increase in taxes because the family moves into a higher tax bracket.

The upshot is that two-income families often have even less income left over today than did an equivalent single-income family 30 years ago, even when they make almost twice as much. And they go deeper in debt. The authors find that it is not the free-spending young or the incapacitated elderly who are declaring bankruptcy so much as families with children.