As many as 374 of the nation’s 381 Metropolitan Statistical Areas - or 98 percent - are currently facing an increased risk of lower home prices through year-end 2010, according to data released Wednesday by PMI Mortgage Insurance Co. (PMI). Albeit, the bit of good news, according to PMI's U.S. Market Risk Index and First Quarter Economic and Real Estate Trends Report, is 212 of the nation’s MSAs hold a minimal-to-low risk of lower prices in two years. Still, 21 of the nation’s 50 largest MSAs are in the highest risk category, signifying the highest probability of lower house prices by the end of the fourth quarter of 2010, relative to the fourth quarter of 2008. “As the recession deepened during the fourth quarter of 2008, increasing rates of unemployment and foreclosures continued to place downward pressure on house price appreciation,” said David Berson, PMI’s chief economist and strategist. “Combined with upward movements in excess housing supply in many parts of the country, these deteriorating conditions are increasing risk of house price declines over the next two years.” Of the nation's 50 largest MSAs, the top three "riskiest" areas, as subject to declining home values, are Miami-Miami Beach-Kendall, Fla., Riverside-San Bernardino-Ontario, Calif., and Ft. Lauderdale-Pompano Beach-Deerfield Beach, Fla. The most stable of the 50 largest MSAs include Pittsburgh, Pa., Cleveland-Elyria-Mentor, Ohio, and Columbus, Ohio. Over the past several quarters, PMI said it has seen the risk rising fastest in the large urban centers across the country, while smaller MSAs have faired relatively better in their current and projected price performance. The report also noted that affordability has improved in many MSAs, as housing prices continued to decline and mortgage rates fell to record lows. PMI’s proprietary “Affordability Index” found affordability improved in the 106 MSAs ranked in the two highest risk categories. For all 381 MSAs, the weighted average affordability reading was 120.6 in the fourth quarter of 2008, compared to a third quarter 2008 reading of 114.5 -- an Affordability Index score exceeding 100 indicates that homes have become more affordable; a score below 100 means they are less affordable. Write to Kelly Curran at Disclosure: The author held no relevant investment positions when this story was published. Indirect holdings may exist via mutual fund investments. HW reporters and writers follow a strict disclosure policy, the first in the mortgage trade.