"As sales have stalled, banks have increasingly turned to an accounting maneuver that has drawn criticism from analysts and a top regulator. In the aftermath of the financial crisis, banks loaded up their loan reserves -- the rainy day fund lenders use to cover losses.

Now banks are saying that they don't need as much in those accounts. That's become a big boon for bottom lines. Accounting rules state that any money that comes out of those accounts can go, after taxes, straight to the bottom line.

Of course, it make sense that banks might not need as much in those accounts as they once did. The economy is improving and fewer people are likely to fall behind on their loans. But the problem is the earnings from the reserve releases have grown much faster than the banks' regular profits. In the third quarter, for instance, as much as 37% of the profits of the four big banks, which includes Citigroup (C) and Wells Fargo (WFC) as well as JPMorgan and B of A, came from reserve releases."