Before revision:  In the case of foreign exchange, Siegel's paradox implies that it is possible to construct foreign exchange models for which the excess rate of return (above the interest rate differential) is positive both for the exchange rate and the inverse exchange rate.
After revision:  In the case of foreign exchange, Siegel's paradox implies that one can construct foreign exchange models for which the excess rate of return (above the interest rate differential) is positive both for the exchange rate and the inverse exchange rate.