ECONOMIC

from differences between lifetime incomes with the inequality that resultsbecause individuals do not earn the same income in successive phases of theirlives.An increase does occur over time, however, in the inequality of income formales 14 years of age and over, and in the inequality of income for all members(male and female) of the labor force. The increasing inequality for allmale workers and all workers results mainly from the greater proportionof workers with part-time and part-year work schedules, rather than froman increase in the inequality of wage rates. The growth of part-time andpart-year work may to some extent be attributed to a shift in industrialcomposition towards the service industries, where flexible hours are morecommon, and partly to the increasing desire among workers for flexibleschedules with shorter hours. Such schedules are particularly attractive tostudents, semi-retired older workers, and married women. Associated withthe increasing importance of these groups in the labor force has been a secularincrease in the variability of annual hours worked and consequently inthe variability of annual income for the labor force as a whole.Since most families (75 percent in 1972) are husband-wife families witha working husband, the stability in the dispersion of adult male incomes hasbeen one factor leading to stability in the distribution of family income. Theincrease in the proportion of wives with earned income evidently did notlead to increases in the relative inequality of family income, partly becausehusbands' and wives' annual earnings have not been positively correlated.In the future, if a strong positive correlation between husbands' and wives'annual earnings should develop, this correlation could be a factor in increasingthe relative income inequality among families.Stability of Income Inequality Among Adult MalesIt is striking that there has been no change in the relative inequality ofincome among adult males. The greater opportunities for schooling amongpersons at all income levels and the larger subsidies for training less advantagedpersons might have been expected to reduce earnings inequalityin the past 20 years, but the relation between equal access to training orschooling and earnings inequality is not so straightforward.The post-World War II period has brought a narrowing of differences inyears of schooling among adult males, and this alone generally decreases theinequality of lifetime income. In the same period, however, the level ofschooling has greatly increased. A recent study suggests that at higher levelsof schooling the relative dispersion of wage rates tends to be greater than atlower levels, and that the effects on income inequality of the higher level andof the smaller variance in years of schooling have somewhat offset each other.Greater equality of opportunity could also lead to increases in income inequalityif investments in schooling or training became more closely relatedto ability. Generally, more able people receive a higher money return on anequal investment in education. In a world where financial access to schoolingand training depend on family income (and assuming that family income and527-867 O - 74 - 10141