The FDIC Deposit Insurance Fund reserve ratio. From the Quarterly Banking Profile:

The Deposit Insurance Fund (DIF) balance increased by $7.2 billion during the third quarter to -$8.0 billion (unaudited), the third consecutive quarterly increase following seven quarters of decline. Assessment income of $3.6 billion and a $3.8 billion negative provision for insurance losses were the primary contributors to the improvement in the DIF balance. Interest earnings, combined with unrealized gains on available-for-sale securities and other net revenue, boosted the balance by another $0.3 billion. Operating expenses reduced the balance by $0.4 billion.

The DIF’s reserve ratio was -0.15 percent on September 30, 2010, up from -0.28 percent at June 30, 2010, and up from -0.16 percent one year earlier. Forty-one FDIC-insured institutions with combined assets of $13.9 billion failed during third quarter 2010, at an estimated cost of $2.3 billion. For the first three quarters of 2010, 127 insured institutions with combined assets of $83.3 billion failed, at a currently estimated cost to the DIF of $19.4 billion.

Improvement!

I feel the need to point out that this isn’t the same as cash on hand, and doesn’t account for the “Full Faith and Credit of the US Government” bit backing your deposits.

(chart lifted from the QBP)