Identification. The name "Nasioi" has been employed by Europeans since the beginning of the twentieth century, and it is best thought of as a linguistic term. Speakers of the Nasioi language and its dialects have referred to themselves by many names, usually reflecting locality. "Kietas" is now commonly heard from other Bougainvilleans and missionaries.
Location. Nasioi occupy a large part of the southeastern portion of the island of Bougainville, from the coast around the port of Kieta inland for approximately 29 kilometers, between 6° and 6° 12′ S. Their villages extended from the coast through the valleys up to altitudes 900 meters above sea level. Thus they occupied several different ecological niches; this settlement pattern conditioned exchanges of produce before European contact and created differential impacts of colonialism and social change. Mean annual temperature at sea level is 27° C, and the temperature varies over a wider range during a 24-hour period than in terms of monthly mean variation. Temperature is estimated to decrease with altitude at a rate of about 3.5° per 300 meters. Rainfall of approximately 300 centimeters annually is distributed more or less evenly throughout the year.
Linguistic Affiliation. Nasioi and Nagovisi form the Nasioi Family in the Southern Bougainville Stock of Non-Austronesian languages. The language includes several distinct dialects and a number of villages contain speakers of other languages as well. Today, most younger people speak Tok Pisin (the lingua franca of Papua New Guinea) and/or English.
Demography. In 1963, Nasioi speakers were estimated at 10,654. There has been a sharp growth in Bougainville's population since that time, and annual natural increase is estimated at close to 4 percent. Although the 1980 census for the island does not distinguish among language groups, a figure of 14,000 may be extrapolated for Nasioi.