@rperezmarco Sorry, but if USD and CHF are both 0 then CHF/USD and USD/CHF are not defined. Let A be a unit of account so USD/A = 0 and CHF/A = 0 then USD/CHF=(USD/A)/(CHF/A)=0/0! @nntaleb applies his valuation argument to  as a *security* (not currencies)