USD is a promise to pay a dollar to the bearer of the receipt. A dollar is an amount of gold, and so is a franc, a pound, a baht, and probably many others. Conversion of a thing into itself is <i>not</i> a conversion. There is no risk free rate, and the behavior of capital constrained by worldwide tax hunt cannot reasonably be called 'natural'. One more thing: banks can only have reserves <i>after</i> covering the totality of their demand deposits, which means that virtually all public banks are insolvent... You say they can sell some assets to cover? Fine! Let's see the selling, and see how many come out alive! I'm waiting!