In any effort for social improvement it is necessary to know conditions that make both for and against success. This is especially so in social hygiene, for it is closely related to all aspects of modern life. Lack of education and false instruction are largely responsible for sexual immorality. It is not so generally known that economic conditions are responsible for vice, opinions on this matter ranging all the way from a denial that economic conditions have anything to do with vice to the assertion that vice would disappear with the increase in the incomes of working-people. Assuming that ignorance is the fundamental cause of vice (an assumption which does not "stand to reason") the results of ignorance must manifest themselves through the institutions of society. Some institutions, such as slavery, encourage vice. Likewise, any caste system, such as feudalism in the Middle Ages, in which there must be depths as well as heights, supplies the vicious classes. The aim of this chapter is to show that, while modern economic conditions do not create "the social evil" they furnish an environment favorable to its spread. If this is so, an improvement in these conditions must accompany all other measures for the eradication of vice. One of the most significant facts of the industrial evolution of the last half-century is the increase in the number of women who have become wage-earners outside the home. According to the Federal Census the number of females fifteen years of age and over, employed as breadwinners in 1900, was 5,007,069, an increase of 34.9 per cent over the number thus employed in 1890.[2] The largest number in any one occupation, 1,213,828, were servants and waitresses. Of this class the domestics were not employed "outside the home." The homes, however, were not their own, and salutary influences of home life do not exist for the majority of domestics. In the decade between 1900 and 1910 the increase in the number of wage-earning women has been even more accelerated than in previous decades, and to-day probably from 8,000,000 to 10,000,000 women in the United States are industrially employed.