High lending standards that make it virtually impossible for millions of younger, single home buyers to get a mortgage are creating an older, more married and wealthier population of homeowners.

The latest Profile of Home Buyers and Sellers by the National Association of Realtors found that dual income households comprise a greater portion of the housing market and singles are declining. Sixty-five percent of all buyers are married couples, 16 percent are single women, 9 percent single men, 8 percent unmarried couples and 2 percent other; percentages of single buyers were slightly higher in 2011.

However, just two years ago, 58 percent of buyers were married, 20 percent were single women, 12 percent single men and 7 percent unmarried couples; the overall market share of single buyers declined a total of 7 percentage points over the past two years. Before 2010, the market shares moved within a very narrow range, generally a percentage point or two.

The study shows the median age of first-time buyers was 31 and the median income was $61,800 in 2011. The typical first-time buyer purchased a 1,600 square-foot home costing $154,100, while the typical repeat buyer was 51 years old and earned $93,100. Repeat buyers purchased a median 2,100-square foot home costing $220,000. First-time home buyers had a 39 percent market share in the past. Long-term survey averages show that four out of 10 buyers are typically first-time buyers, who are critical to a housing recovery because they help existing home owners to sell and make a trade.

Mortgage approvals have improved slightly in recent months but about half the national adult population has a credit score too low to get a loan. Median scores for adults in the prime first time buyer age groups, 25-34 and 35-44 are far below the median scores of FHA and conventional purchase mortgages being approved today.

The September closing rate for applications for mortgages to purchase a home was 61 percent, the highest approval rate for purchase loans all year. The median FICO score for all conventional purchase mortgages closed in September was 762 and for FHA purchase mortgages, popular among first-time buyers because of their low down payment requirement and used by 46 percent of first-time buyers in 2011, was 701, according to Ellie Mae, whose software platform processes about 20 percent of all U.S. mortgage originations.

The national median FICO score is 723 today, but median scores for younger adults are considerably lower. For ages 25-34, the median is 652 and for the 35-44 age group, it’s 659.

Paul Bishop, NAR vice president of research, said the study is painting a clearer picture of the impact of mortgage limitations. “We’ve known for some time that stringent mortgage credit standards have been holding back home sales, but these findings show single buyers have been hurt the most over the past two years. Total home sales would be 10 to 15 percent higher without these unnecessary headwinds,” he said.

“The continued growth in married couples as single buyers shrink demonstrates that households with dual incomes are more successful in obtaining a mortgage. However, given the historically favorable housing affordability conditions, most single-income buyers could also purchase a home and stay well within their means, if lending requirements were more sensible,” Bishop said.