During the 1970s, many women changed their minds about whether they would leave the labor force after marrying and having children or whether they would be in the labor force most of their adult lives. In 1968, the National Longitudinal Survey asked a representative sample of women aged 14 to 24 whether they expected to be in the labor force at age 35. Twenty-nine percent of white women and 59 percent of black women responded that they expected to be in the labor force at that age. In fact, when these women were 35 years old, 60 percent of those who were married and 80 percent of those who were unmarried were in the labor force. In other words, many more women ended up being in the labor force than expected to be when they were of high school and college age. What effect did this fact have on the earnings of these women? Briefly explain.