A new study by the Munich economic institute Ifo and the University of Oslo found that women's incomes drop by an average of 20 percent after marriage, primarily due to reduced working hours or complete resignation from professional work. This effect occurs independently of childbirth. Gender roles play an important role in the decision to reduce working hours and contribute to the income decline of married women. The structure of the tax system in Germany is a key reason for the reduction in women's working hours after marriage. Under the income splitting for spouses, both partners' incomes are taxed jointly, which benefits couples with large income differences.