Forest Transition theory is based on the empirical observation that as income (Economic Status) rises within poor countries, deforestation increases up to a certain point, but then begins to decrease (Commons Condition Trend). Posited reasons include relative prices and scarcity (i.e. in poor countries, agricultural land tends to be highly desirable, even if not very productive, so farmers may clear forests to practice subsistence agriculture. But then as economic development increases, subsistence farmers may abandon land in favor of migrating to urban areas with better economic opportunities, while industrial demand for wood drives up prices and encourages commercial forestry) or policy (i.e. people may demand better forest protections, forest dwellers may gain more rights, or government policies may shift towards encouraging forest product imports and conserving domestic forests). The proximate causes in this theory are not well understood, but economic status is widely seen as an underlying variable.