Metro areas across the country posted a second consecutive month of home price increases in May, according to the latest S&P/Case-Shiller Home Price Indices, released today. Sixteen of the 20 metropolitan statistical areas (MSAs) tracked showed improvements. Both composites also gained, the 10-city rising 1.1% from April and the 20-city up 1.0%.

Unfortunately, that data is not seasonally adjusted, and "virtually all the pickup looks seasonal," said David Blitzer, chairman of S&P’s Index Committee, in a Q&A discussing the numbers. With seasonal factors taken into account, the 10-city composite’s gain was reduced to a 0.1% increase and the 20-city remained flat.

Compared to April, 11 MSAs and both composites saw their annual rates worsen in May. Year over year, 19 MSAs and both composites showed declines, the 10-city and 20-city indices dropping 3.6% and 4.5% respectively.

Overall, larger cities seem to be faring better. Washington, D.C., continues to be the only metro area to show an annual improvement, up 1.3%. Los Angeles, New York, and Boston all tied for the somewhat bittersweet distinction of showing the smallest loss on an annual basis, a decline of 3.2%. These cities also show the largest improvement since 2000, Blitzer said. Meanwhile, Detroit, Tampa, and Las Vegas delivered new post-peak lows in May.

However, even while both of the previous two months’ gains have been muted once seasonal factors were brought into account, those improvements still hold some significance, said Chip Case, a member of the S&P Index Advisory Committee, while taking questions regarding the numbers. "There is a big difference between bouncing along a downward drift and bouncing along a rocky bottom," he said. "Basically all the numbers we’ve seen over the past six months—starts, existing sales, new sales, and so forth—have been flat. The fact that prices in a repeat sales index and using a three month moving average actually went up, it seems to me, says something important."

Indeed, Robert Shiller, economist and co-founder of the Case-Shiller Index, has improved his predictions of price declines going forward, after warning last February that the market might see a drop of between 10% and 25% in the coming years. "The recent data lowers the probability of that scenario a little bit, but I still worry about it," he said.

When asked which factors are most telling when determining the future direction of the housing market, Shiller listed recent trends in home prices as No. 1, followed by the employment situation and survey measures of home buyer confidence. Confidence levels, however, seemed to be a particular point of concern—a situation the looming debt ceiling deadline is doing little to help. "The aggregate economy is at a turning point and there is much uncertainty now."

Claire Easley is a senior editor at Builder.

Learn more about markets featured in this article: Washington, DC, Detroit, MI, Las Vegas, NV, Tampa, FL, New York, NY, Boston, MA, Los Angeles, CA, Greenville, SC.