The classic article about liquidity premiums is Kessel [3]. Kessel regresses the liquidity premium, measured as the difference between the forward rate and the actual future spot rate, against the current spot rate and observes a positive relation between the level of the current spot rate and the size of the liquidity premium. Olsen alters Kessel's model in two respects. First, he introduces a proxy for risk or uncertainty about interest rates as an additional determinant of the liquidity premium. Second, instead of using the actual future spot rate as a measure of the expected future spot rate, he specifies the expected future spot rate as a linear combination of the current and past spot rates.