U.S. wheat production doubled between 1950 and 1975. Improved yields per acre accounted for most of the increase. Since 1974, however, the growth in U.S. wheat yields per acre has leveled off. About half of the U.S. wheat crop is exported, but the somewhat erratic nature of foreign demand has caused considerable instability in the U.S. wheat industry. Large carryovers have been a problem in most years since 1950, despite Government programs to regulate wheat acreage, subsidize producers, store wheat, and facilitate wheat exports.