Motherhood is the primary cause of the gender pay gap. This gap in pay reflects a gap in productivity between men and women with children. This productivity gap explains about two-thirds of the wage gap between men and women. However, women with no children, especially younger women, outperform men yet still earn lower wages
Researchers have long studied the gender pay gap, attributing this divergence to such factors as educational and career choices by women, psychological differences between men and women regarding risk and reward, demand for work flexibility, and, of course, discrimination, among other issues.
However, this research reveals that two-thirds of the pay gap can be explained by a productivity gap between men and women that is driven by motherhood. About 8 percentage points of the 12 percent residual pay gap between men and women can be explained by lower workplace productivity of mothers. Prior to motherhood, women are actually more productive than men and their productivity climbs again as their children age to equal that of men. However, for women who choose to have children, the fall-off in workplace production is enough to impact their pay and, possibly, the earnings of younger women whom employers assume will have children.
Researchers have come to call the decrease in wages for mothers a “child penalty.” The contribution of this work is to determine how much of that penalty is explained by productivity differences in the workplace. This productivity difference may arise from differences in the effort, extra (undocumented) hours worked, or effectiveness of men relative to women. While on average, the pay gap is quite close to the productivity gap, this is not true over all of the lifecycle. In particular, women without children are estimated to be as productive—if not more productive—than men without children, but they are still paid less than these men. Mothers, on the other hand, are substantially less productive than fathers and are paid commensurate with this productivity gap.