 In 1922 Fisher wrote that this and the Jevons were the two best unweighted indexes based on Fisher's test approach to index number theory.The ratio of harmonic means or "Harmonic means" price index is the harmonic average counterpart to the Dutot index.The Marshall-Edgeworth index, credited to Marshall (1887) and Edgeworth (1925), is a weighted relative of current period to base period sets of prices.