Liberal structural reforms associated to changes in the export product composition may affect economic growth, and at the same time, may yield biases in the official standard trade index numbers from developing countries and error measures in the real rate of economic and exports growth. This paper proposes a set of index numbers which incorporates the export product composition in a standard export index in such a way that changes in the current export value can be decomposed into: price changes; quantity changes, and product composition changes. In the applications of those indexes for the Peruvian case, it is found that the estimated overvaluations in the official annual average rate of growth of the real exports value and the GDP, were, respectively 3% and 0.6%, for the period 1993-2004.