The median annual income for women included in the study, which looked at over 16,000 Stockholmers born in 1985, was 248,000 kronor ($26,600), compared to the figure of 341,000 for men.
That was despite the fact that 41 percent of the women had undergone at least three years of tertiary education, while the figure for men was just 27 percent.
“It's a problem in and of itself that men are lagging behind women in education. But regarding income, when women start to work, they don't receive any benefit from [having more education]. Women with upper secondary level education earn less than men without it, that's disheartening,” Per Bark, head of analysis at the county administrative board behind the study, told Dagens Nyheter, which was first to report on the results.
Bark said he was “quite surprised” at the size of the discrepancy.
The study was carried out between 2000 and 2016, and by the end of that period, 16,200 of the original 19,300 participants still lived in the Swedish capital.
Of those, women in the group earned an average of 90,000 kronor less each year than the men, even when other factors such as socio-economic background, sickness and other kinds of leave, and education were taken into account.
Women without upper secondary education typically earned the lowest salaries, with a median annual income of 109,000 kronor, while men without upper secondary education earned 271,000 kronor.
This was not only more than double the income of women with equivalent education, but also more than women with at least three years of tertiary education.
Gender wasn't the only factor that seemed linked to stark income differences. The study also looked at the difference between Stockholmers born in Sweden or abroad, which neighbourhood they lived in, whether they had disabilities, and education level. Stockholmers who were born overseas, had foreign-born parents, or came from a socio-economically disadvantaged background, were less likely to have upper secondary education, which was linked to earning a lower salary at the age of 31.
However, parental level of education seemed to be a more important factor than whether someone was born in Sweden or abroad, when it came to predicting whether they would complete upper secondary education.
Bark suggested that investments in education could be a way of evening out these inequalities. “If we can succeed with education and entry to the job market, that means big achievements over time,” the analyst said.