Apartments have been filling up for the past year. And judging from the REITs' first-quarter conference calls, a lot of the people in those apartments might have been home buyers just a few years ago.

Consider the numbers. Homeownership fell to 66.5 percent nationally. “Homebuying continues to drop,” says David Neithercut, CEO of Chicago-based Equity Residential, in the company’s first-quarter conference call, transcribed on “They're enjoying the lifestyle. They can rent a better lifestyle than they can afford to buy. They're in great cities with great jobs. And consider the alternatives. They're not going to sink every penny that they can beg, borrow, and steal into a home.”

The REIT first-quarter numbers across the board reflected this trend, as many saw move-outs to buy homes (as a percentage of the people moving out) hit historic lows. Houston-based Camden Property Trust reported that 10.4 percent of move-outs were for home purchases vs. 10.5 percent and 10.6 percent in the past two quarters, which was the all-time low. The company’s high was 23 percent in 2004, and its long-term average is around 17 percent.

Birminghan, Ala.-based Colonial properties Trust saw its move-outs for home purchases drop to 13 percent, which was just off of its all-time low of 12.9 percent in the first quarter of 2009. Denver-based UDR’s move-out rate for homeownership fell to 11 percent in its first quarter. Arlington, Va.-based AvalonBay Communities saw its number fall to 12 percent (from 15 percent last quarter and historically in the mid-20 percents). And Rochester, N.Y.-based Home Properties saw its move-outs for home purchases fall to 9.5 percent.

Even in cities like Phoenix, which has historically high move-out rates for home purchases, companies are seeing people continue to choose to rent. Equity reported that its move-outs for homes in that city was 16.7 percent, which is historically low.

“The weakness in the for-sale market may provide an obvious and direct benefit to the rental market with households that are increasingly choosing to rent versus buying,” says Bruce Blair, CEO of AvalonBay on the company’s first quarter conference call.

The question is, how long will the trend continue? In Washington, D.C., for instance, a recent report said that condo ownership now makes more sense than renting an apartment.

On the other hand, UDR CEO Tom Toomey thinks the rental market is poised to grab an even bigger share of the market. One reason is the oft-repeated mantra of demographics. “The college kids are not even interested in the market,” he says. “They’re the primary renter cohort, and they’re going to be in an urban setting where their jobs are. They’re not aspiring to be home owners right now.”