Although central banks hold a small share of the stock of America's external liabilities, they have become big marginal buyers.

ECONOMIST: Forever free | The

Italy might not need to leave the euro on grounds of its net external liabilities, and its primary budget (ie, before interest payments) is under control.

ECONOMIST: The Merkel memorandum

The FROB had ordered external valuations, which found that their liabilities far exceeded their assets.

WSJ: Spain Brings the Pain to Bank Investors

Since the external costs likely grow with bank size, it probably would make sense for the fee to grow with liabilities.

FORBES: Huntsman's Good Idea: Tax Giant Financial Institutions