California's economy as a whole is the largest of any state in the United States and is the fourth largest economy in the world. The Northern California megaregion is home to the Silicon Valley with major corporations such as: Cisco Systems, Apple Inc., Oracle, EBay, Yahoo!, Facebook, YouTube, Google, and Hewlett Packard, the San Francisco Financial District (home to headquarters of various financial and business firms such as VISA, Wells Fargo, and Union Bank of California and is the largest financial district outside New York City), Wine Country, and much of the Central Valley which is one of the world's most productive agricultural areas, producing 8% of the nation's total crops. The centers of major national government offices, such as the United States Court of Appeals for the Ninth Circuit, the Federal Reserve Bank of San Francisco, and the U.S. Mint, as well as the California State Capitol and the California Supreme Court are all located within the region. The Bay Area also has the largest concentration of multi-millionaire households of any metropolitan area in the country and the largest concentration of billionaires of any U.S. metropolitan area, almost more than the next three metropolitan areas combined.