The largest asset on Uncle Sam's balance sheet is not U.S. Official Reserve Assets, nor Total Mortgages, nor Taxes Receivable.

The correct answer, as of the latest Flow of Funds report for Q1 2012, is ... Student Loans.

The rapid growth in student debt has been a frequent topic in the financial press.

One stunning chart that caught my attention illustrated the rapid growth in federal loans to students since the onset of the great recession.

Here is a chart based on data from the Flow of Funds Table L.105, which shows the Federal Government's assets and liabilities.