Human capital theory does not rule out non-monetary concerns. A few others suggested Conscientiousness, which one might argue is different from ability. I gave these close to full credit. A few others argued that Ph.D.'s would earn more in the future. All else equal, the rate of return on education will be lower for a women who plans on taking a few years off from work to have children.
Education raises earnings for people who work.
If a woman takes time off from work, she captures the wage premium of education for fewer years. In 4-6 sentences, answer both of the following questions. Use diagrams if helpful. In mining, force alone is sufficient to make people work hard at their job. It is easy to judge ability, and force people to work up to their ability.