Corporations pay a lower effective tax rate than Warren Buffett and Mitt Romney, but you wouldn't know it from all the complaints that our corporate tax rate puts our country at a competitive disadvantage. Despite an official corporate tax rate 35 percent, last year, U.S. corporations paid just 12.1 percent of their earnings in federal corporate income taxes. Buffett's tax rate is 17.4 percent; Romney's reported 2010 tax rate was 13.9 percent. Our broken tax system blesses U.S. multinational corporations with lots of loopholes that enable them to pay less in taxes than Main Street businesses. It has starved our government of revenue. Contrary to common perception, U.S. corporations pay far less toward the cost of public services and infrastructure than they did in decades past, and less than foreign competitors pay in their countries today. In the 1950s, corporate federal income taxes accounted for nearly one-third of federal government revenue; in 2011, corporate taxes accounted for less than 8 percent. U.S. corporate profits account for more than 10 percent of GDP, a 50-year high. Federal corporate income taxes collected as a percent of GDP are at a 50-year low. The challenge of corporate taxes and competitiveness is not that rates are too high, but that loopholes, preferences and subsidies make corporate tax collections far too low.