Economic activity in the Federated States of Micronesia consists primarily of subsistence farming and fishing. The islands have few mineral deposits worth exploiting, except for high-grade phosphate. Long line fishing of tuna is also viable with foreign vessels from China that operated in the 1990s. The potential for a tourist industry exists, but the remoteness of the location and a lack of adequate facilities hinder development. Financial assistance from the U.S. is the primary source of revenue, with the U.S. pledged to spend $1.3 billion in the islands in 1986–2001; when the Compact was amended in 2004, the United States committed to providing $110 million in development aid through 2023. The CIA World Factbook lists high dependence on U.S. aid as one of the main concerns of the FSM. Geographical isolation and a poorly developed infrastructure are major impediments to long-term growth.