Banks have been hit with another big, scary number in the battle to end 'too big to fail': $1.2 trillion. This is the headline number for how many bonds the world’s biggest lenders need to meet rules unveiled on November 9.

In reality, however, many European and US banks don't have a big hole to fill to meet requirements for bonds that can take losses or be converted into equity. Legal changes in much of Europe, or natural replacement of maturing senior debt with bonds that are only marginally different, will get them most of the way there.