  Siegel's paradox is a fundamental question in international finance about
exchange rates for futures contracts and has puzzled many scholars for over
forty years. The unorthodox approach presented in this article leads to an
arbitrage-free solution which is invariant under currency re-denominations and
is symmetric, as explained. We will also give a complete classification of all
such aggregators in the general case. The formula obtained in this setting
therefore describes all the negotiated no-arbitrage forward exchange rates in
terms of a reciprocity function.
  Keywords: Siegel's paradox, forward exchange rates, discount bias.
