James Hamilton, professor at the University of California, has counted the U.S. public debt at request of the National Bureau of Economic Research. According to the White House official reports, the national debt constitutes $16.4 trillion, while to Hamilton's estimates, this figure is much higher - $70 trillion. The economist considered not just state liabilities, which advisors to the president are talking about, but also different federal programs, which are financed by the taxpayers. “Housing, other loan guarantees, deposit insurance, actions taken by the Federal Reserve, and other government trust funds” in order to stabilize the economy, where also taken into account while calculating. The biggest portion came from Social Security and Medicare, which make $26.5 trillion and $27.6 trillion respectively. Professor Hamilton reminded the government that “the U.S. population is aging, and an aging population means fewer people paying in and more people expecting benefits”. Besides, the huge Treasury debt is triggered by the general disappointing economic situation in the world. Unfortunately, that level is not a “freezing point”. Boston University Professor of Economics Laurence Kotlikoff thinks that the actual debt amount is much greater – more than $200 trillion. While the specialists are trying to determine the exact number, S&P downgraded America's credit rating to AA+ from AAA.