Researchers at the Federal Reserve Bank of New York this month released a report probing the decline in consumer debt since the economy went into recession at the end of 2007.

The drop is undeniable, but some wags have worried that the shift is attributable largely to a surge in mortgage defaults and therefore of little consequence in terms of consumer behavior.

But the Fed researchers say U.S. consumers “are indeed reducing their debts at a pace not seen over the last 10 years,” with a particularly marked shift coming on nonhousing debt.

Fed economists Meta Brown, Andrew Haughwout, Donghoon Lee and Wilbert van der Klaauw note that during the bubble years, consumers boosted their debt by an average of $130 billion a year.

But they started trimming their debt in 2008, when the financial sector nearly collapsed under the weight of the Lehman Brothers bankruptcy, and knocked $140 billion off their tab last year.

What’s more, the shift toward saving from borrowing is even more pronounced if you focus on nonmortgage borrowing, which the Fed says is easier to track than housing-related debt because of the vagaries of calculating the effect of home resales. Brown et al. write:

Until 2009, consumers were increasing their non-mortgage debt obligations each year. In 2009 net borrowing other than mortgage was a small negative ($13 billion). Since consumers had been borrowing an average of over $200 billion per year between 2000 and 2007, this indeed looks like a change in behavior.

An upbeat reading of the study suggests Americans are quickly adjusting to leaner times. The researchers promise to study just why this is so.

A remaining issue is whether this frugality is a result of borrowers being forced to pay down debt as credit standards tightened, or a more voluntary change in saving behavior. In future work, we intend to study these questions in more detail.

But the bottom line is that strapped Americans have no choice, writes Gluskin Sheff economist David Rosenberg.

He notes in his Monday market comment that household net worth has plunged by $12 trillion since the bubbly days of 2007.

That’s decline almost 10 times as large as the net worth increase spurred by this fall’s QE2-inspired stock market rally, for those of you who have been questioning Fed chief Ben Bernanke’s embrace of the so-called wealth effect.

“As the realization sets in to households that this loss of wealth is permanent, and that not even recurring quick fixes by the government and the Federal Reserve can stop human nature in its tracks, then what happens is that the changes in consumer behavior become more entrenched,” writes Rosenberg.