Import substitution inustrialization (also called ISI) is a trade and economic policy based on the premise that a country should attempt to substitute products which it imports (mostly finished goods) with locally produced substitutes. Even though ISI is a development theory with links to dependency theory, and not naturally a trade theory, its political implementation and theoretical rationale are rooted in trade theory. Baer contends that all countries which have industrialised after the United Kingdom went through a stage of ISI where the large part of investment in industry was directed to replace imports (Baer, pp.95-96).