 Of the population in the municipality, 851 or about 45.2% were born in Alterswil and lived there in 2000.There were 623 or 33.1% who were born in the same canton, while 242 or 12.9% were born somewhere else in Switzerland, and 98 or 5.2% were born outside of Switzerland., children and teenagers (0–19 years old) make up 26.2% of the population, while adults (20–64 years old) make up 60.2% and seniors (over 64 years old) make up 13.6%.