This thesis examines the cross-sectional and time series variation between commodities futures prices and current prices. The 'Theory of Storage' states that the difference between the two prices will be a function of two factors: The first is the cost of storing the commodity over the term of the futures contract (carrying costs). The second factor is the value of the convenience yield. The convenience yield is a concept which evolved from the theory of storage and is explained as the benefit

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... hich accrues to the individual or firm that holds the commodity in storage but does not accrue to the holder of the futures contract. It is generally assumed that the value of a commodity's convenience yield is decreasing in the aggregate inventory available and some indirect empirical support has been generated for this assumption, however, an economic model has not been provided which derives the result. There are two objectives of this thesis: The first is to provide a model of the convenience yield which explains the relationship between the level of inventories and the value of the convenience yield. The second objective is to empirically test the predictions of the model. The model provided shows the convenience yield to be decreasing in the level of aggregate inventory. In addition, the value of the convenience is found to be related to the time-series process of shocks to demand. An analogy is drawn between the convenience yield and an option with a stochastic exercise price. Using futures price data and aggregate inventory data, the empirical implications of the model are tested. The results support the hypothesis that a commodity's convenience yield is decreasing in aggregate inventory. Some evidence is also provided that the convenience yield is decreasing in the correlation between shocks to demand.