The forward rate unbiasedness hypothesis states that the current forward rate should be an unbiased forecaster of the future spot rate. Inference has always been done under the assumption that the forward premium is a stationary short memory series. Recent empirical results have indicated that this assumption is not valid. https://www.jmannino.com/super-price-Mint-Smash-Mighty-Vapors-Salts-30mL-flash-find/