DATA relating to the size distribution of income in the United States, fragmentary as they are,2 support the thesis that income is more equally distributed today than it was during the prewar period. Although families at the very lowest income levels do not appear to have gained appreciably in the redistribution of income, there can be little doubt that the middle-income families have gained at the expense of the wealthiest families. The share of the income received by the top fifth of the nation's families and single persons decreased by I2 per cent between I935-36 and I948, whereas the share received by the middle three-fifths increased by I4 per cent during the same period (Table i). What factors account for this