Senators Byron Dorgan (D-North Dakota)  and Carl Levin (D-Michigan) deserve some credit for being smart enough to go to the GAO and ask a sensible question when they commissioned a <a href="http://www.reuters.com/article/bondsNews/idUSN1249465620080812">recent study</a> on why more than two thirds of foreign corporations and about half of the domestic companies doing business in the US get away with not paying corporate taxes in any given year.