NPR's John Ydstie reports on Federal Reserve Board chairman Alan Greenspan's assessment of the U.S economy. Greenspan appeared before the House Banking Committee yesterday. He said the economy remains strong owing to increases in productivity by American workers...but if and when that falters, inflation could be the result. He cautioned that doesn't necessarily mean an interest rate hike is in the cards. Greenspan also said the prudent thing to do with the current surplus would be to pay down the national debt, which would boost economic capacity.