The Commerce Department reported last week that the personal savings rate fell near to a record low in October, when American households saved a meager two-tenths of 1 percent of their disposable income. The rate implies that a family with take-home pay of $40,000 saves on average $1.50 a week.

The average American household now spends 13 percent of its after-tax income to pay debts, the highest percentage since 1986. Much of it goes to pay home mortgages and car loans, but the average American household is also carrying more than $8,000 in credit card debt.

While some blame materialist consumers armed with a credit card, Elizabeth Warren, a Harvard Law School professor, points to environmental constraints.

Today’s middle-class families with two working parents, she said, have far less financial leeway than a single-income middle-class family of 30 years ago. What Ms. Warren classifies as “fixed costs” – mortgage, child care, health insurance, car and taxes – take up 75 percent of the income of today’s two-income family. By contrast, the those costs represented about half of a middle-class family’s income in the early 1970’s.