All of the explanations for the differences between unleaded and leaded gasoline margins are fairly straightforward, though some may be difficult to distinguish empirically. This section presents each theory and explains how it might lead to the pattern of margin differences that was observed in the 1980s. Section 3 discusses the data and presents some summary statistics about the buyers and prices of leaded and unleaded gasoline. In Section 4 I derive and implement a test of the price discrimination hypothesis.