Agriculture contributed 29.9 percent of GDP in 1999, and in 1996 employed 34 percent of the labor force. In terms of GDP this proportion has been fairly consistent through the 1980s and 1990s, despite fluctuations
As in most Pacific countries, subsistence production for domestic use is an important part of the economy, although not well recorded. The export of agricultural products has been highly unpredictable over time. Through most of the 20th century, Tonga's main export was coconut products, mainly copra (dried coconut meat yielding coconut oil), but at various times other products have been exported in sizeable quantities, particularly bananas.
A specialized market for squash was established in the 1980s when Tonga secured a quota to supply the vegetable to Japan during several months of the year when other sources, especially New Zealand, were not producing. In the early 1990s, this source of export income grew, but in the second half of that decade, production fluctuated considerably as a result of disease, weather, and oversupply. Other squash producers from Vanuatu and Mexico have also offered competition by entering the same market.
Other agricultural products, such as bananas and market vegetables, are significant in the domestic market but have contributed very little to export income in recent years. Even vanilla beans, which were significant exports in the early 1990s, have declined in importance because of international competition. There has been a small but steady export of root crops, mostly to supply Tongan and other Pacific communities, especially in New Zealand. Kava (a mild legal narcotic) production has increased recently, and this has considerable export potential as illustrated by the success of this industry in Vanuatu.
Fish was the second most important export during the 1990s, mainly high-grade tuna and snapper. The potential sustainable harvest of tuna is about 30,000 tons a year, which is several times higher than the existing harvest. Most fish is exported unprocessed to the United States, Fiji, and American Samoa. A cannery in Tonga is under consideration, but a restraining factor is government legislation requiring that 90 percent of sales from such a venture would have to be to overseas buyers.