Married Swedish men don’t have the same problem and also earn more coin than married or co-habiting Swedish women.

According to the study, a single woman’s income bottoms out once she ties the knot or co-habits, whereas a married man’s income goes from strength to strength.

In the study men who had been single in 1990 and 1993 but lived together with someone in 1998 had 14.8 percent higher income levels than men who were single for all three years. Women in the same situation earned 8 percent less.

Married women with a university degree have an easier time closing the income gap but still have lower income prospects than single women. When couples start to have children, the inequality gap really widens.

In the study, Saco’s chairperson Anna Ekström and Saco’s economist Håkan Regnér point out that women are punished when they start a family whereas men’s salaries often get a boost.

Employers expect women to take more responsibility in the home, and therefore reward them less economically. Women spend more time at home, and men work more, thus widening the inequality, the study says.