boundaries. Oregon restricts the development of farm and forest land. The regulations are controversial: some economic analysis has concluded that farmland lying immediately outside of Portland's growth boundary is worth as little as one-tenth as much as similar land located immediately on the other side; other analysis have found that the UGB has no effect on prices when some other variables are taken into account. Oregon's law provides that the growth boundary be adjusted regularly to ensure adequate supply of developable land; as of 2018 the boundary had been expanded more than thirty times since it was created in 1980. In the Metro area, the urban growth boundary has to have enough land within it for 20 years of growth; it is reviewed every six years. Other cities in Oregon seek regulatory review of proposed urban growth boundary expansions as needed. Washington's Growth Management Act, modeled on Oregon's earlier law and approved in 1990, affected mostly the state's more urban counties: as of 2018, Clark County, King County, Kitsap County, Pierce County, Snohomish County, and Thurston County. In Tennessee, the boundaries are not used to control growth per se, but rather to define long-term city boundaries. (This was a response to a short-lived law in the late 1990s allowing almost any group of people in the state to form their own city). Every county in the state (except those with consolidated city-county governments) has to set a "planned growth area" for each of its municipalities, which defines how far out services such as water and sewer will go. In the Memphis area, annexation reserves have been created for all municipalities in the county. These are areas that have been set aside for a particular municipality to annex in the future. Cities cannot annex land outside of these reserves, so in effect the urban growth boundaries are along the borders of these annexation reserves. Additionally, new cities are only allowed to incorporate in areas determined to be planned for urban growth. California requires each county to have a Local Agency Formation Commission, which sets urban growth boundaries for each city and town in the county. States such as Texas use the delineation of extraterritorial jurisdictional boundaries to map out future city growth with the idea of minimizing competitive annexations rather than controlling growth. Notable U.S. cities which have adopted UGBs include Portland, Oregon; Boulder, Colorado; Honolulu, Hawaii; Virginia Beach, Virginia; Lexington,