The number of improved U.S. local housing markets edged down in August, indicating that the housing recovery has tapered its momentum, a leading industry report showed on Tuesday. The number of improved markets in August dipped to 247, down from 255 in July, according to the Improving Markets Index (IMI) released by the National Association of Home Builders (NAHB). But the figure was still more than triple that of August 2012. The \"pace of improvement is being hampered somewhat by challenges that builders and buyers are experiencing with regard to the availability of credit, materials, lots for development and labor,\" said NAHB Chairman Rick Judson. The IMI traces housing markets throughout the country that are showing signs of improved economic health, employment growth and housing price appreciation. A metropolitan area must see improvement in all three measures for at least six consecutive months before being included on the list. \"As house prices return to more normal levels in fully recovered markets, further IMI advancements will be more modest,\" explained NAHB Chief Economist David Crowe.