Equilibrium real exchange rate is defined as a rate, which is consistent with simultaneous achievement of internal and external equilibrium. Internal equilibrium is a situation where the non-tradable goods market clears, while external equilibrium is achieved when the current account is sustainable. Real exchange rate misalignment is a gap between actual and equilibrium real exchange rate and is a sustained departure of the real exchange rate from its long run equilibrium value (Zhang, 2001, Edwards, 1989a, 1989b and Asfaha and Huda, 2002).
According to Edwards (1988) pointed, the real exchange rate is expected to provide signals to economic agents in the economy. Information on the extent to which the real exchange rate diverges from its equilibrium level serves as a guide to policy makers to ensure that the real exchange rate does not send wrong signals to economic agents. Wrong signals can result in inefficient resource allocation and lead to the reduction of the country’s welfare. Misalignment of the real exchange rate could increase economic instability, distort investment decisions and result in welfare and efficiency costs. According to Edwards (1989a:12) real exchange misalignment especially overvaluation hurts exports and can wipe out the agricultural sector. It can also cause capital flight, which may be optimal from a private perspective but a substantial cost in terms of social welfare.