U.S. housing starts rose less than expected in May, likely reflecting labor and material constraints, but the overall trend remained consistent with strength in the housing market, the government reported Tuesday. The Commerce Department said housing starts rose 6.8 percent last month to an annual rate of 914,000 units from April\'s pace of 856,000 units. Economists had expected starts to increase to a rate of 950,000. Permits for future construction activity fell in May, but they had surged in April to above the 1 million mark. The decline last month was due to the volatile multi-family category; permits for single-family construction hit their highest level in five years.