Before pricing in a rapid economic recovery, investors might consider the fundamentals of the economy's workhorse -- the U.S. consumer.

Despite recent frugality, consumers have barely dented their debt load. The Federal Reserve will offer a fresh peek at that mountain on Thursday, when it releases its "flow of funds" data for the first quarter.

By the end of 2008, households were on the hook for $13.8 trillion in debt -- nearly matching the $14.3 trillion output of the entire U.S. economy, not adjusted for inflation, that year.

Households are shedding debt; they're just not doing it very quickly. They owed roughly 130% of disposable income at the end of 2008, down only slightly from a record 133% in the first quarter of 2008.

An old saw about U.S. consumers is never to underestimate their willingness to spend beyond their means. The debt-to-income ratio first crossed 100% during the 2001 recession, when debt-fueled consumer spending helped spark a recovery. It kept rising post-recession as super-low interest rates encouraged still more borrowing. And it rose even after the Fed raised rates, as consumers piled into mortgages to chase rising home prices.

Money is easy again, but unemployment is far higher and wage growth slower than at any time during the 2001 recession.

Households have also now suffered the bursting of two bubbles -- housing and stocks -- carving $12.9 trillion from their net worth since the second quarter of 2007. The recent market rally should bolster household balance sheets, the flow of funds data might show. But real estate is still the biggest household asset, at 36% of net worth, and prices haven't stopped falling.

Finally, credit is still far tighter than at any point during the 2001 recession, according to a Citigroup index of financial conditions.

"Without stronger financial underpinnings, growth will likely be narrowly based and not dynamic, and deflationary undercurrents will persist," Citi economist Robert DiClemente recently wrote.

Credit should improve, but the era of easy credit is over, suggesting household debt could fall closer to a mere 100% of disposable income. That could sap at least $3 trillion in household borrowing from the economy -- hardly a recipe for a V-shaped recovery.