Questions about the levels and about what instruments would count towards the total add to banks' anticipation about a long list of new rules that haven't been fully implemented, or that regulators are still writing.
The Fed alone is working on four more rules: to raise more capital for systemically important banks, to require banks to invest in assets they can easily sell, to balance the maturities of assets and liabilities, and to make the short-term funding market less susceptible to panics.
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One of the reasons that Wells Fargo is behind some of the other banks is that it has traditionally relied on client deposits for funding, and simply did not need to borrow money from other banks or from investors.
While clients can quickly withdraw deposits, they are still considered "sticky"—meaning banks don't anticipate that depositors will withdraw their funds all at once—and the Fed may take that into account by granting banks such as Wells Fargo more leeway when setting its long-term debt requirement.
"We would not be surprised if there are some differentiations between the banks based on their business models. But that's an assumption, that's not an information," De Longevialle said.
Morgan Stanley and Goldman Sachs have far fewer deposits to fund their business, and they are also the two banks that far exceed the 25 percent thought to be the upper boundary for loss-absorbing capital level.
A senior Fed staffer working on the rule said at a conference last week he would prefer consensus among the world's regulators grouped together in the G-20's Financial Stability Board before the Fed put out its own rule.
Banks in Europe often have a different legal structure than those in the United States, which group all their operating subsidiaries under one holding company, and this may make it hard to agree on a common approach soon.