WASHINGTON – The rebuilding of Americans’ wealth is proceeding in steps rather than strides.

Households’ net worth rose in the January-to-March period, the fourth straight quarterly gain. Yet tumbling stock prices have reduced their wealth since then.

Some economists say Americans’ net worth may now be down slightly for the year. That helps explain why many say it will be 2012 or 2013, at best, before Americans’ wealth will return to its pre-recession levels.

Net worth – the value of assets such as homes, bank accounts and investments, minus debt such as mortgages and credit cards — rose 2.1 percent last quarter, the Federal Reserve said Thursday. It now amounts to $54.6 trillion.

In the midst of the recession, household net worth sank as low as $48.3 trillion. It has since risen 13 percent. Yet even counting last quarter’s gain, net worth would have to rise 21 percent more to regain its pre-recession peak of $65.9 trillion.

Household wealth is vital to the economy because consumers tend to spend according to how wealthy they feel. And their spending accounts for about 70 percent of the economy.

During the recession, sinking home equity and stock prices and job instability made shoppers skittish. Should they become more nervous about their finances, the economic rebound could weaken or stall.

Over the past several quarters, the growth of net worth has been uneven. Last quarter’s 2.1 percent increase exceeded the 0.9 percent increase in the fourth quarter of last year. But it fell well short of the 4.1 percent rise in the second quarter of 2009 and the 5.4 percent gain in the third quarter.

As Americans have gradually recovered some of their wealth, many of them — especially the affluent — have been spending more. But the housing and stock markets remain fragile. That’s why most consumers aren’t spending as freely as they typically do in the early phases of recoveries.

Stock values rose 4.4 percent in the January-to-March period, to the highest point since the second quarter of 2008. But that was before they tumbled in recent weeks. As measured by the Dow Jones U.S. Total Stock Market Index, stock values lost $1.22 trillion in value between March 31 and the close of trading Wednesday.

The sharp decline in the past month and a half threatens the improvements in Americans’ financial security over the past year.

The S&P 500 rose 4.9 percent in the first quarter. April 23 the index had gained 9.2 percent for the year. It was on pace to exceed even last year’s 23 percent surge.

But the S&P 500 has tumbled 11 percent since the high-water mark. That has more than wiped out all of 2010’s gains — it’s down 3 percent for the year and more than 30 percent from its 2007 peak. The result has been shrunken retirement savings accounts and anxiety about spending.

Americans’ home equity isn’t making up the difference, either. U.S. home values dipped 0.4 percent in the first quarter. That was after they had risen 0.2 percent in the final quarter of 2009. In the first quarter, home prices fell 3.2 percent compared with the fourth quarter, according to Standard & Poor’s/Case-Shiller index.