The economy was formerly based on agriculture, mainly sheep farming, but today fishing contributes the bulk of economic activity. In 1987, the government began selling fishing licenses to foreign trawlers operating within the Falkland Islands' exclusive fishing zone. These license fees total more than $40 million per year, which help support the island's health, education, and welfare system. Squid accounts for 75% of the fish taken. Dairy farming supports domestic consumption; crops furnish winter fodder. Foreign exchange earnings come from shipments of high-grade wool to the UK and the sale of postage stamps and coins. The islands are now self-financing except for defense. The British Geological Survey announced a 200-mile oil exploration zone around the islands in 1993, and early seismic surveys suggest substantial reserves capable of producing 500,000 barrels per day; to date, no exploitable site has been identified. An agreement between Argentina and the UK in 1995 seeks to defuse licensing and sovereignty conflicts that would dampen foreign interest in exploiting potential oil reserves. Political tensions between the UK and Argentina rose in early 2010 after a UK company began oil drilling activities in the waters around the Falkland Islands but abated somewhat when the drilling operation failed to discover commercially exploitable oil reserves. Tourism, especially eco-tourism, is increasing rapidly, with about 30,000 visitors in 2001. Another large source of income is interest paid on money the government has in the bank. The British military presence also provides a sizeable economic boost.