Belize has a small, essentially private enterprise economy that is based primarily on agriculture, tourism, and services. The cultivation of newly discovered crude oil in the town of Spanish Lookout has presented new prospects and problems for this developing nation. Besides petroleum, Belize's other primary exports are citrus, sugar, and bananas. Belize's trade deficit has been growing, mostly as a result of low export prices for sugar and bananas. The new government faces important challenges to economic stability. Rapid action to improve tax collection has been promised, but a lack of progress in reining in spending could bring the exchange rate under pressure. The Belize Dollar is fixed to the U.S. dollar at a rate of 2:1. Domestic industry is limited, constrained by relatively high-cost labour and energy and a small domestic market.Tourism attracts the most foreign direct investment although significant foreign investment is also found in the energy, telecommunications, and agricultural sectors. Belize's economy depended on forestry until well into the 20th century. Logwood, used to make dye, was Belize's initial main export. However, the supply outstripped the demand, especially as Europeans developed man-made dyes which were less expensive. Loggers turned to mahogany, which grew in abundance in the country's forests. The wood was prized for use in cabinets, ships, and railroad carriers. While many merchants and traders became wealthy from the mahogany industry, ups and downs in the market had a large impact on the economy. In addition, new mahogany trees weren't being planted, because mahogany trees grow slowly; the rate of natural regrowth necessitated a large, long-term investment in tree farming, which was not made. As the 19th century progressed, loggers were forced to go deeper into the forests to find the trees, increasing labour costs. Variations of mahogany exports over long periods of time were linked to the accessible supply of the resource. Thus, improvements in hauling methods helped the cutters satisfy increasing demands for mahogany by enabling them to extract timber from areas in the interior that had been previously inaccessible to them. Immediately after the introduction of cattle in the early 19th century, tractors in the 1920s, and lorries in the 1940s, production levels rose dramatically. When the supply of accessible timber dwindled and logging became too unprofitable in the 20th century, the country's economy shifted to new sectors. Cane sugar became the principal export and recently has been augmented by expanded production of citrus, bananas, seafood, and apparel. The country has about 8,090 km² of arable land, only a small fraction of which is under cultivation. To curb land speculation, the government enacted legislation in 1973 that requires non-Belizeans to complete a development plan on land they purchase before obtaining title to plots of more than 10 acres (40,000 m²) of rural land or more than one-half acre (2,000 m²) of urban land.