Consumer spending will be in the doldrums for years to come, according to a study from the BlackRock Investment Institute. So don't think consumer spending will help improve the economy any time soon.

Consumer spending is the most important single factor in the American economy. Personal consumption accounts for about 70 percent of the GDP.

Some analysts are too optimistic, according to the BlackRock study.

Many predictions, it says, are "drawn on the selective use of data and has often misapprehended key issues surrounding the topic."

The truth is that consumers remain over-leveraged, wage increases are flat, and plummeting values of homes and other financial assets have exposed consumers' debt problems.

Americans still have a long way to go to reduce debts. "While some progress in consumer debt reduction has been made, the heavy lifting of meaningful deleveraging still lies ahead," BlackRock warns.

If you consider mainly wages and salaries and don’t count other income sources or income of the top incomes, the household debt-to-income ration was about 154 percent for the fourth quarter of 2010, according to BlackRock. That's much worse than the 100 percent debt-to-income ratio cited by other researchers.

Consumers have reduced their debt level by only 7.5 percent since the recession, the study asserts, not by 12 percent that many researchers cite.

In past decades, rising values of home and other financial assets masked high levels of consumer debt. That's all gone now.

"Recent dramatic reversals in these trends," the study states, "argue for difficult times ahead for consumer spending and the ability and willingness to draw on credit."

High unemployment continues to weigh down consumer spending, and the number of dual-income households, which boosted consumer spending in the past, has dropped 9 percent from its peak.

Poor consumer spending will remain a drag on the economy for some time, BlackRock concludes. "The U.S. consumer may now be in store for a sustained period of relative austerity and slow deleveraging that will result in very modest economic growth rates for years to come."

Consumer confidence levels also point to low consumer spending.

Consumer confidence was at its lowest level since November 2008 last month. The confidence level, as measured by the Thomson Reuters/University of Michigan preliminary index of consumer sentiment, increased from 55.7 last month to 57 this month.

"Volatility in equity markets and the lack of hiring is weighing on the already fragile consumer psyche," Aaron Smith, a senior economist at Moody’s Analytics Inc. told Bloomberg. "Also, consumers are seeing little relief at the pump as gasoline prices have been little changed over the past several weeks."