NEW YORK (CNNMoney) -- The economy is still struggling. And Americans are in for a long and painful adjustment period.
One major reason: their own household debt.
Many experts say private debt owed by households, as well as businesses, is an even bigger problem than the government debt that's getting so much attention lately. And it won't be solved without a difficult stretch of high unemployment and slow growth that will likely last for six or seven more years, producing America's own version of Japan's "Lost Decade."
"I think it's one of the major headwinds we're fighting against right now," said David Wyss, a visiting fellow at Brown University and former chief economist at Standard & Poor's.
Following a real estate bust that hit Japan in the 1990s, the economy fell into a prolonged period of economic stagnation that lasted for years and became known as the country's 'Lost Decade.'
In the U.S., the situation is shaping up to be similarly stubborn.
"I think we're in for a lot of disappointment," said Carmen Reinhart, a senior fellow at the Peterson Institute for International Economics and a leading expert on financial crises. "If historic norms hold, deleveraging isn't pretty, and it is not a smooth process. We're already four years into this. I don't think the next six years look great."
The bubble economy that led to the recession was fueled by American consumers, businesses and banks taking on too much debt, particularly in real estate, during the decade before the crisis.
Total private sector debt -- held by consumers and businesses combined -- peaked at 283% of gross domestic product in early 2008 -- nearly three times the size of the entire economy.
The good news is that since the recession, consumers have been paying off debt and saving more. Private debt fell to 234% by the end of last year, though much of that decline resulted from bad mortgage debt shifting from banks to the government through the bailout of mortgage finance giants Fannie Mae and Freddie Mac, Reinhart said.
But even with some modest improvement in savings in recent years, households still can't afford the current debt levels, which are well above the average disposable income.
"At least households are being prudent and rational and bringing the debt down. But I worry we'll see it leveling off higher than I think it should," said Wyss.
That's the major reason why it will be more difficult for Americans to start spending again as they did coming out of past downturns when they had only a fraction of current debt burdens.
Without a jump in consumer spending, the economy is unlikely to really get going again. And until that happens, Americans can expect to see lingering high unemployment and additional suffering in the years ahead.
"The engine-of-growth role that [consumer spending] played in earlier recoveries is unlikely in this one," Reinhart said.
Stephen Roach, the chair of Morgan Stanley Asia, wrote a recent note suggesting that American consumers were turning into "zombie consumers," greatly because "burdened with underwater mortgages, excessive debt, and subpar saving, U.S. consumers are stretched as never before."
And the process of unwinding those huge debt loads is slow going.
Despite Americans paying down debt, saving more of their paychecks, and shedding some of their debt through bankruptcy and foreclosure, Reinhart estimates that the amount of consumer debt alone has declined to only about 92% of the gross domestic product.
That's down from only 98% at its high point at the end of 2007 -- a peak that shot up from less than 70% in 1999.
"The deleveraging process doesn't really get underway quickly," Reinhart said.
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