In From the Valley to the Summit: The Quiet Revolution That Transformed Women’s Work, Claudia Goldin informs that
…in the early to mid-1960s the labor force plans of young women, 14 to 21 years old, reflected the current labor market work of their mothers, their aunts, and possibly their older sisters. The expectations of young women regarding what they planned to do when they were 35 years-old were more in line with what older women were currently doing than with what the younger women would actually be doing in 15 to 20 years. Their expectations about their future employment were inconsistent with what they eventually did. But in the late 1960s and the early 1970s something began to change. Young women (14 to 21 years old) when asked by the NLS Young Women (1968) what they would be doing at age 35 began to offer answers that were more consistent with their actual futures. In 1968, independent of their age at the time, about 30 percent said they would be in the labor force at age 35. But in 1975 about 65 percent said they would be [see figure].
This change in labor market expectations was accompanied by an increase in educational investment and radical changes in educational concentrations as women shifted from majors that were job- or consumption-oriented to those that rewarded long-term investment in a career.
So what was the main driver behind those changes? According to Goldin, it was the birth control pill:
…the Pill lowered the costs to young, unmarried women of pursuing careers, particularly those involving substantial, upfront investments of time. The Pill fostered women’s careers in two ways. A young college woman in the mid-1960s who was considering whether or not to enter a program involving a considerable investment in her time had to factor into this decision its impact on her personal life (e.g., social life, marriage chances after the career investment period). Sex was highly risky in a world without a highly effective, female-controlled, and easy to use contraceptive such as the Pill. A pregnancy could derail a career. The Pill had a direct effect by reducing the risk, and thus the cost, of having sex. The Pill also had an indirect effect because it led to an increase in the age at first marriage and thereby produced a “social multiplier” effect. The Pill virtually eliminated one potent reason for early marriage and for many of the social trappings (e.g., going steady, engagements) that led to early marriage. With more men and women delaying marriage for many years after college graduation, the decision of any one woman to delay marriage to pursue a career meant that she would reenter a marriage market that would not be as depleted.
via The NBER Digest