Subsistence and Commercial Activities. The Siwai have long been horticulturalists. Until World War II the horticultural system was dominated in every way by taro ( Colocasia esculenta ) of which there were more than fifty different kinds. Other root crops such as yams and sweet potatoes were also grown, alongside sugarcane, bananas, and various green vegetables. Tree crops, including coconuts, breadfruit, sago, and almonds, were important, pigs were of major significance (for exchange and feasting), and fish and prawns were taken from small streams. Taro constituted about 80 percent of the diet. Taro blight ( Phytopthora colocasiae ) wiped out taro in the early 1940s and, despite constant attempts to regenerate taro, sweet potatoes now dominate the horticultural system as taro previously did. In the postwar years, Siwais attempted to withdraw from plantation labor and establish their own commercial agricultural system. Rice, always a prestigious food, was widely grown; peanuts, corn, and coffee were also tried but a lack of access to markets prevented commercial success. Cocoa was introduced at the end of the 1950s. Construction of roads to the Buin coast in the 1960s and across the Mountains to the east coast in the 1970s enabled cocoa marketing to become increasingly successful. After experiments with other forms of commercial agriculture, mainly cattle farming, cocoa is now the sole commercial crop and is planted and marketed by almost all households. Cash income is primarily generated from cocoa sales, vegetable sales in markets within Siwai, some local wage and salary employment, and the Remittances and expenditure of Siwais working at Panguna and elsewhere.
Industrial Arts. Few artifacts are currently produced in Siwai. Pottery manufacture effectively ended not long after World War II. Finely woven baskets of different kinds—known as "Buka baskets," though almost all are made in Siwai—are produced on a significant scale by several village households and sold extensively in Bougainville and beyond.
Trade. In the nineteenth century there was considerable precontact trade and intermarriage with the nearby Solomon Islands. One significant traded item was shell money, brought from Malaita in the Central Solomon Islands. Trade with European traders began before the end of the nineteenth century, and it increased in the 1920s and 1930s, with monetization and missionization. European trade largely replaced trade with other Melanesians, though shell money continued to be traded until recent years. In 1956, a Siwai Rural Progress Society was established to market cocoa, copra, and other local commodities; the society grew rapidly in the 1960s and 1970s but collapsed as individual producers traded Directly with east coast wholesalers. Most villages have at least one trade store.
Division of Labor. Horticulture was and is women's work, and women worked in the gardens four times as much as men in the early decades of this century. Men spent some time in the gardens, undertook arduous clearing activities, hunted, were responsible for garden magic, and organized ceremonial activities. The introduction of sweet potatoes reduced the necessity for long hours of horticultural work for the women. Cash crops became male activities, garden magic disappeared, and time spent on ceremonial activities declined. Many men and some women are now employed inside Siwai, but even more of the people work outside Siwai at the mine and in the towns.
Land Tenure. Throughout Siwai, land is owned by matrilineages. Every matrilineage owns full or residual rights to tracts of garden land or potential garden land and most matrilineages claim ownership of more distant hunting areas or fishing streams. Land was sold in certain exceptional circumstances, and some rare tracts of land are now individually owned. Men conducted agricultural activities on their wives' land, and high levels of cross-cousin marriage previously ensured the integrity of tracts of matrilineage land. High Population densities, nontraditional marriage, and cocoa cultivation have increased the complexity of land tenure and inheritance.