SThe detailed crude oil refinery input data that is available for U.S. refineries is not available for the rest of the world, but OECD data is available for refinery output of residual fuel oil and crude runs, which will help to explore if refinery capacity constraints had a major impact.
	SOutside the U.S., there is still a considerable volume of bottoms material in refineries that is not being converted to lighter product.  As a result, if the world crude oil slate had seen a significant decline in gravity in 2004, one would have expected residual fuel oil yields to increase.
		–The U.S. leads the world in residual fuel destruction.  Residual fuel production is only about 5%of total product production, but we still have some refiners without bottoms processing running some fraction of heavier crude oils and producing residual fuel.
		–In Europe and in Asia there are many refineries with no bottoms processing and a number of countries that produce 20 – 30% of their product as residual fuel oil.
	SThis graph shows that residual fuel oil yield did not increase, implying that the amount of heavy crude oil being added to meet growing demand was not enough to noticeably affect refinery yields, and therefore was probably not a major factor in determining light-heavy crude oil price differences.