Several states have established groundwater management districts and limit the development of new wells, in an effort to slow the rate of depletion in a largely agricultural region that depends on irrigation. Some states also require farmers to measure and report the volume of water they withdraw from the aquifer each year, thus generating helpful data for state agencies, while also increasing farm-level awareness of the rate of aquifer depletion in the region. Several states and the federal government have embraced the concept of water marketing, and public agencies have implemented services to facilitate water sales and leases in recent years. In theory the market price of water reflects current supply and demand conditions, thus motivating farmers and other water users to consider the opportunity cost of water when choosing how much to purchase and apply.