U.S. economic growth is slowing as the two-year housing decline worsens amid the surge in foreclosures and the collapse of more than 100 mortgage companies, said David Berson, chief economist of Fannie Mae, the largest mortgage buyer. The Federal Reserve today lowered its benchmark rate to 4.75 percent, the first cut in four years, saying the ``tightening of credit conditions has the potential to intensify the housing correction and to restrain economic growth.''