Big banks in the U.S. enjoy an implicit subsidy worth between $15 billion and $70 billion because of the perception that the government will not allow them to fail, according to the International Monetary Fund.

The IMF, an international organization that promotes cooperation between countries, is the latest to weigh in on the question of whether U.S. banks remain "too big to fail" in the wake of the financial crisis and subsequent financial reform legislation.

In an update to its global financial stability report for April, the IMF indicated that U.S. banks, as of 2013, are able to obtain funding more cheaply because investors believe that in the event of failure, the government will offer the banks support.

The IMF measured the subsidy for banks identified by the Financial Stability Board as "systemically important" three ways, including comparing bond yields at banks thought to be too big to fail to bond yields at others, examining the price of insurance on different banks' bonds and studying the ratings' agencies appraisals of the chances that a bank would receive government support in case of a failure.

Some of those methods suggest that the "too big to fail" subsidy enjoyed by big banks is declining, but it still remains sizable. "This at least partially reflects tighter regulations and more effective supervision," according to the report.

The phenomenon appears to be even larger in other advanced countries, by the IMF's assessment. Implicit subsidies for systemically important banks total $25 billion to $110 billion in Japan, $20 billion to $110 billion in the United Kingdom and up to $90 billion to $300 billion in the euro area.

The IMF's results follow a report released last week by the Federal Reserve Bank of New York finding that U.S. megabanks were too big to fail as of 2009 and that large banks engage in riskier activities.

Some bank representatives and analysts have pointed to other evidence to make the case that large banks no longer receive a subsidy based on the promise of government support. In particular, the ratings agency Moody's said in November that it expected failing bank-holding companies to be resolved without support from the government thanks to the financial regulatory regime put in place in 2010.