I The self-employed consist of two distinct groups, farm operators and nonfarm group usually referred to as urban self-employed. The number of farm operators varied from a low of 4,510,000 in January 1947 to a high of 5,474,000 in July. (Monthly Report of Labor Force, Population Division, Bureau of Census; Current Population Reports, Labor Force, P-57, Bureau of Census.) The number of individuals who were farm operators at some time during 1947 is estimated by Federal Security Agency at 6,400,000. The number of urban self-employed was 6,015,000 in November 1947 (Current Population Reports, Labor Force, P-57, Bureau of Census). The number at some time during 1946 is estimated by Federal Security Agency at 7,200,000. Prior to World War II there was a gradual increase in number of urban self-employed. Since war, however, number has increased quite markedly, possibly as much as 25%, as veterans and other new entrants to self-employment have started establishments of their own. In 1940, according to Reports on Population, Bureau of Census, about 35% of urban self-employed were in retail establishments, 23% in service trades, 12% in construction work and 11% in professions. The remainder were found in approximately equal proportions in manufacturing, transportation, insurance and real estate, and wholesale establishments. (16th Census of United States: 1940, Population, Vol. III, The Labor Force, Part 1, Table 78.) 249 STAT. (1935) 620, 622-625. 3 Report of Committee on Economic Security, H. R. Doc. No. 81, 74th Cong., 1st Sess. (1935) 25. This committee which was established by Executive Order No. 6757, June 29, 1934, to study feasibility of adopting a social security program in this country was not unmindful of fact that self-employed persons were also in need of old-age insurance protection. For such persons as well as for other groups not covered under a compulsory system, it recommended the establishment of a related, but distinct, voluntary system of Government old-age annuities, ... . Ibid. at 21. A similar proposal was made by President in his message to Congress recommending enactment of social security legislation. Message of President Recommending Legislation on Economic Security, H. R. Doc. No. 81, 74th Cong., 1st Sess. (1935) vi. Provision for purchase