Americans are smoking less than any time since 1942. The Agriculture Department says cigarette use dropped 5 percent in 1989, the largest decline in six years. And the trend is expected to continue. Overall, American smokers consumed about 533 billion cigarettes last year, the department's Economic Research Service said Monday. Exports, however, jumped 20 percent to 142 billion cigarettes. Annual use by the U.S. adult population dropped 7 percent to an average of 2,888 cigarettes, the report said. Economist Verner Grise said that was the lowest average since 1942, when the average was 2,585 cigarettes per adult. The peak was 4,345 cigarettes in 1963, before beginning its longtime decline. The average is for all Americans 18 years and older, smokers and non-smokers alike. It is a statistical comparison only and does not indicate the actual smoking habits of the population. ``Domestic cigarette consumption will probably continue to fall this year because of higher prices, increased restrictions on where people can smoke, anti-smoking activity and declining social acceptance of smoking,'' the report said. Meanwhile, the report said total U.S. tobacco output could increase substantially this year, perhaps by 8 percent over the 1989 crop of 1.4 billion pounds. However, smaller on-hand inventories will reduce total supplies for 1990-91.