There are many questions about why women earn less than men, despite gains in education and skills.  One factor contributing to the gender pay gap is incentive pay.  A new report from the ADP Research Institute (ADP RI) found that women, on average, earn a 17 percent ($15,000) lower salary than men.  However, when factoring in bonus pay where there’s a 69 percent gender pay gap, the total earnings pay gap widens to 19 percent ($18,500).  In addition, the report discovered that young women, aged 20 to 30, fared the worst with a 21 percent less bonus-to-base ratio compared to male colleagues.  Women with a low starting salary started jobs with a near-equal base pay of men; however, the base salary gap worsened for them after six years.