This paper explains the existence of intersectoral wage differential in a developing economy in terms of trade union behavior in the formal sector industry and analyzes its role in predicting the outcomes of trade and investment reforms on welfare. It provides theoretical explanations of certain real life phenomena e.g. why the developing countries are yearning for foreign capital despite the standard immiserizing result and why these countries are not reducing the tariff rates beyond certain levels although they have chosen free trade as their development strategy.