Subsistence agriculture occurs when farmers grow crops on smallholdings to meet the needs of themselves and their families. Subsistence agriculturalists target farm output for survival and mostly for local requirements. Planting decisions occur principally with an eye toward what the family will need during the coming year, and only secondarily toward market prices. Tony Waters, a professor of sociology, defines "subsistence peasants" as "people who grow what they eat, build their own houses, and live without regularly making purchases in the marketplace".