The Central Valley is one of the world's most productive agricultural regions. More than 230 crops are grown there. On less than 1 percent of the total farmland in the United States, the Central Valley produces 8 percent of the nation's agricultural output by value: US$43.5 billion in 2013. California's farms and ranches received almost $50 billion in cash receipts for their output in 2018. The Central Valley's agricultural productivity relies on irrigation from both surface water diversions and groundwater pumping from wells. About one-sixth of the irrigated land in the U.S. is in the Central Valley.