Many industrialized western countries depend on imported foreign crude. In 1977, for example, the United States imported 46% of its oil and petroleum products, chiefly from Saudi Arabia, Iran, and other OPEC nations. By September 1, 1983, the United States imported only 28% of its oil. The chief suppliers were Mexico, with 826,000 barrels per day, Canada, with 479,000, and Venezuela, with 419,000. Saudi Arabia is now seventh on the list of suppliers for the United States. This shift is responsible for the trend toward a heavier crude supply mix on the international market. Transportation fuels and petrochemical feedstocks are in increasing demand; hence many refiners would like to get out of the fuel oil business, More “bottom-of-the-barrel” conversion capability will be required in many refineries to efficiently process these heavier feedstocks and maximize production of light products.