The most important exports are petroleum and petroleum products, natural gas, chemicals, steel products, and fertilizer. Trinidad possesses sizable oil and gas reserves, and its prosperity is linked directly to the production of petroleum and petrochemicals. A peaking of petroleum production in the late 1970s and the decline in worldwide petroleum prices in the 1980s caused economic problems. However, increased exploitation of the country's natural gas reserves since the 1990s, as well as rising prices for oil, petrochemicals, and liquified natural gas, have caused an economic boom. The islands also have a significant tourist industry. Agriculture employs a smaller proportion of the population than industry and services; agricultural products include cocoa, rice, coffee, citrus fruit, and flowers. The main trading partners are the United States, Jamaica, and Brazil.