“In the 1990s, the term “maternal wall” emerged from academe (Swiss & Walker, 1993) and quickly gained traction in the popular press, in part because it helped explain the somewhat unexpected and enduring problem of pay disparity between men and women– a problem that did not disappear when women entered the workforce in large numbers, as most experts had expected. The “motherhood penalty” is estimated to be between 3 and 10% of earnings (Anderson, 2003; Avellar & Smock, 2003; Budig & England, 2001).” (Williams)
Williams, J. (n.d.) Family responsibilities discrimination. Retrieved from WorkLife Law: http://www.worklifelaw.org/