The agrarian expert Professor Oganovsky estimated that by 1927 some to per cent. of peasant farms in the western districts had introduced improved rotation, and that by 1932 this proportion could be expected to have increased to 20 or 25 per cent. Professors Oganovsky and Weinstein in 1927–8 hazarded the estimate that yield per acre might increase in the near future at a rate of 2 per cent. In 1924 the membership of agricultural co-operatives was officially given as between 2 and 3 million, or about 10 per cent. of all peasant households. In 1914 it was estimated that the number of peasant households was between 18 and 19 millions; in 1928 there were more than 25 million. Meantime the rural population had increased by less than 15 per cent., so that the increase of farms was mainly due to a larger number of persons successfully claiming the right to hold land.