In a theoretical survey, Vollrath (1991) discussed and compared the theoretical foundations of
alternative indices of RCA. The survey examined ten indices including export performance
indices (Balassa-type index), net export index (UNIDO-type index), and Vollrath‟s indices.
He concluded that the most satisfying measures are Balassa‟s index and the relative export
advantage measure (one Vollrath‟s index), with the difference between them being negligible
for low levels of commodity aggregation and/or for small countries in terms of share in
world‟s commodity.