Even though the financial crisis happened more than five years ago, there remains a clear reminder of it on the balance sheets of Regions Financial (NYSE:RF) and Huntington Bancshares (NASDAQ:HBAN), two of the nation's largest regional banks.

The evidence is tucked away in one of the least discussed areas of their balance sheets: retained earnings. This line item reflects a bank's rolling balance of earnings that aren't distributed to shareholders via dividends or used to repurchase common or preferred shares. It's located in the equity section of the balance sheet and contributes to both capitalization and overall size.

In the majority of cases, this number is both positive and growing. Take Wells Fargo (NYSE:WFC) as an example. By the beginning of 2010, it had retained a combined $41.6 billion in earnings. Fast-forward to the end of last year, the figurative account held $92.4 billion, equating to an increase of 132%.

The reason retained earnings typically head higher is because most banks make money most of the time. In the off chance that they don't, however, this number can potentially dip into negative territory. More specifically, if a bank's net loss in any period exceeds its balance of retained earnings, then the account will turn negative and thereby subtract from, as opposed to add to, a bank's capital base.

And this is the unenviable position in which Regions Financial and Huntington Bancshares find themselves. As you can see in the chart above, both of these companies' retained earnings dropped below zero at the time of the financial crisis. Regions' fell in the fourth quarter of 2008 while Huntington's passed the threshold in the first quarter of 2009.

By this measure, these banks are the worst performers among the nation's largest lenders. The average big bank grew its retained earnings by 11.6% since the beginning of 2008. Meanwhile, Regions' and Huntington's balances have dropped by 149% and 284%, respectively. It's no coincidence, in turn, that their share prices remain two of the most deeply depressed in the industry since the crisis.

Although it's tempting to conclude that this has no bearing on the present, as the losses occurred years ago, nothing could be further from the truth. "No one has the right to not assume that the business cycle will turn," warns big bank CEO Jamie Dimon. "Every five years or so, you have got to assume that something bad will happen." Consequently, let this serve as a gentle reminder.

John Maxfield has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Wells Fargo. It also owns shares of Huntington Bancshares and JPMorgan Chase. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.