Soil erosion has both on-farm and off-farm impacts. Reduction of soil depth can impair the land's productivity, and the transport of sediments can degrade streams, lakes, and estuaries. Since 1933, soil conservation policies have existed in the United States. Originally they focused on the on-farm benefits of keeping soil on the land and increasing net farm income. Beginning in the 1980s, however, policy goals increasingly included reductions in off-site impacts of erosion. As a consequence of conservation efforts associated with explicit U.S. government policies, total soil erosion between 1982 and 1992 was reduced by 32% and the sheet and rill erosion rate fell from an average of 4.1 tons per acre per year in 1982 to 3.1 tons per acre in 1992 while the wind erosion rate fell from an average of 3.3 tons per acre per year to 2.4 tons per acre per year over the same period. Still, soil erosion is imposing substantial social costs. These costs are estimated to be about $37.6 billion annually. To further reduce soil erosion and thereby mitigate its social costs, there are a number of policy options available to induce farmers to adopt conservation practices including education and technical assistance. financial assistance, research and development, land retirement, and regulation and taxes.