Iowa Senator Tom Harkin was a dissenting vote as the Senate approved a fourth term for Federal Reserve chairman Alan Greenspan Wednesday. Harkin questioned Greenspan’s method of controlling the economy by raising interest rates.The Fed hiked the nation’s key interest rates by a quarter percent Wednesday and indicated more increases are on the way. Harkin, a democrat from Cumming, says that’s wrong in an economy that’s moving along.Harkin says Congress has a chance to use the budget surplus to make some important investments. He says that won’t happen if rising interest rates put the brakes on things.Harkin says the economy is better left alone.The Federal Reserve says inflation is a danger to the economy, but Harkin says inflation isn’t increasing enough to worry about.