EZRA KLEIN echoes a line of thinking that's increasingly common:

If you take the Rogoff/Reinhart thesis seriously -- and people should, and increasingly are -- what distinguishes crises like this one from typical recessions is household debt. When the financial markets collapsed, household debt was nearly 100 percent of GDP. It's now down to 90 percent. In 1982, which was the last time we had a big recession, the household-debt-to-GDP ratio was about 45 percent. That means that in this crisis, indebted households can't spend, which means businesses can't spend, which means that unless government steps into the breach in a massive way or until households work through their debt burden, we can't recover. In the 1982 recession, households could spend, and so when the Federal Reserve lowered interest rates and made spending attractive, we accelerated out of the recession.

I agree that debt is a problem, but not for the reasons Mr Klein cites. Debt levels have been extraordinarily high for the last two decades, and yet for most of that time households and businesses had no problem spending. Debt alone doesn't restrain spending; it's the burden of debt relative to incomes that can put a chill on outlays. The big problem for households is that incomes have fallen below levels that were expected at the time debt was taken on. And incomes are expected to stay below that level for some time; indeed, nominal incomes are falling ever farther behind the pre-crisis trend.

Nominal incomes are entirely within the control of the Federal Reserve. Mr Klein cites the early 1980s as a different recovery. Was it a different recovery because debt levels were lower, or because total nominal income—nominal GDP—rose by roughly 10% in 1983 and 1984, rather than a 3.85% pace in 2010 and slightly slower in the first half of 2011? Nominal income is entirely under the control of the Fed, but the Fed seems more willing to generate fast NGDP growth when it can do so by cutting interest rates than when it is forced to use other tools. That doesn't let it off the hook, however.

Americans are no doubt somewhat poorer than they thought they were, in real terms. As a result, high household debt levels are bound to have an impact on household spending—though not, obviously, on the economy as a whole. With growth in its current, depressed state, thanks largely to the Fed's timidity, we simply can't say that debt constraints are the big economic problem. To too great an extent, the impact of debt simply reflects the Fed's acceptance of weak nominal growth, preventing us from drawing any clear conclusions.