The tightening of credit that has troubled financial markets in recent months also will affect the U.S. economy, former Federal Reserve (Fed) Chairman Alan Greenspan said Wednesday. Greenspan, speaking at the World Business Forum in New York City, said U.S. home prices almost certainly would drop and that the housing slump will eventually force consumers to reduce spending. “When you get house prices flattening out, you begin to get pressures on consumption,” Greenspan said, adding that rising stock prices could help offset declining home values.