Sales of existing homes nationwide decreased 12.9 percent in April to 5.05 million units compared to the 5.8 million units reported during the same time last year, according to a recent report from the National Association of Realtors (NAR).

The decrease in existing homes sales is largely attributed to the surge of sales in April and May of 2010 in response to the homebuyer tax credit, according to a statement.

"Given the great affordability conditions, job creation and pent-up demand, home sales should be stronger," said Lawrence Yun, NAR chief economist. "Although existing home sales are expected to trend up unevenly through next year, unnecessarily tight credit is continuing to restrain the market, along with a steady level of low appraisals that result in contract cancellations."

The national median existing home price for all housing types was $163,700 in April, a 5 percent decrease from April 2010, according to a statement. Distressed homes – typically sold at a discount of about 20 percent – accounted for 37 percent of sales in April, up from 33 percent in April 2010.

First-time homebuyers purchased 36 percent of homes in April, down from the 49 percent in April 2010 when the tax credit was in place. Investors rose to 20 percent in April from 15 percent in April 2010. The balance of sales was to repeat buyers, which were 44 percent in April.