Multifamily permits surpassed the sector's construction rate for the last three quarters of 2011, while single-family construction remained flat.

Prior to the housing collapse, the country built five to six times more single-family homes than apartment buildings, said Polina Vlasenko, a fellow at the American Institute for Economic Research. Today, that ratio is about three to one.

New permits for multifamity buildings doubled since mid-2009, and permits exceed completions by a healthy margin. Most of the increase in overall housing permits results from the construction of multifamily structures, as shown below.

The relationship between new building permits, an approximation of future construction, and completed housing units indicates whether a market is booming, flat or retracting. When the number of permits is above the number of units completed, as it was for most of 2011 in the multifamily sector, construction will probably increase.

"The slide in homebuilding moderated at the end of the recession, but it has not yet recovered," Vlasenko said. "Now the tide seems to be turning."

Builders should expect to build even fewer houses than they are now, she said. Construction of single-family homes — a much bigger segment of the housing market — has not stabilized much. The number of new permits for single-family homes has hardly changed since mid-2009, and, unlike the multifamily sector, the number of homes completed still slightly exceeds permits, a sign that construction of single-family home will fall.

Vlasenko says housing construction is beginning to add to the overall economy.

"New residential investment contributed positively, if modestly, to the growth of GDP for the last three quarters of 2011. We have not seen growth of this kind since 2005," she said.

However, the investment doesn't seem to be translating to job growth.

Overall construction employment in January rose by 21,000 to 5.57 million from 5.55 million. But only 2,500 of those were residential construction jobs, 61% less than the 6,400 nonresidential construction jobs added in January.