As a result of the crisis and various government rescue efforts, the largest six banks in our economy now have total assets in excess of 63 percent of GDP (based on the latest available data). This is a significant increase from even 2006, when the same banks’ assets were around 55 percent of GDP, and a complete transformation compared with the situation in the United States just 15 years ago, when the six largest banks had combined assets of only around 17 percent of GDP.Note that's 63% of GDP, not 63% of bank deposits. And this:
The big four have half of the market for mortgages and two-thirds of the market for credit cards. Five banks have over 95 percent of the market for over-the-counter derivatives. Three U.S. banks have over 40 percent of the global market for stock underwriting.The chart of bank mergers (enlarges with a click) comes via Mother Jones.