Women, take today off! In fact, take the rest of the year off!

Danish unions representing more than 1.1 million private and public employees, at least half the country's workforce, are urging women members to do just that — and only half in jest — to protest a 17 percent pay gap to men.

"It's a way to remove the gender pay gap in a split second," Lise Johansen, head of the campaign for the Danish Confederation of Trade Unions, said in a telephone interview. "Go to a tropical island for the rest of the year!"

While "everyone knows it's a joke," the protest, now in its fifth year, highlights the challenges Denmark faces even as it ranks among the countries with the smallest pay disparities, Johansen said.

Scandinavian countries have been the most successful in closing the gender gap, the World Economic Forum said in a report last week. Denmark ranked No. 5 in the study of 142 countries, trailing Iceland, Finland, Norway (where the government has recently made military service mandatory for women) and Sweden.

Yet in terms of wage equality for similar work, Denmark ranked 38th, according to the report. The biggest pay differences exist for white-collar workers such as architects and lawyers, as well as science and technology professionals, where women earn 24 percent less than men on average, according to the Danish statistics agency. The second-biggest gap is in the finance industry, where women make 22 percent less than men, it said.

Average hourly wages for Danish women trail those of men by almost a fifth even as more women hold higher degrees than men, according to the confederation. The group is one of five unions organizing the protest "Women's Last Work Day." The gap reflects structural discrepancies in the Danish labor market, and shrinks to about 7 percent when salaries for the same job are compared, Johansen said.

"We still have a gender pay gap, and women here are the best educated in the world, and better than men," Johansen said, citing the forum's study. "Why should you be paid more to change the oil of a car than to nurse kids?"

Women probably won't heed the union's advice and will instead just treat their colleagues at work to cake, she said, referring to a Danish tradition of bringing pastries to the office the day before a vacation starts.

Denmark, where about three-quarters of all private and public employees belong to a union, will from January require companies with 10 or more employees to conduct a so-called gender audit to compare salaries of women and men.

The requirement broadens a previous guideline that applied only to businesses with 35 or more employees, to capture most of the labor force. It also allows union representatives to discuss results, according to the confederation.

"We hope that more transparency can do something about the gender pay gap," Johansen said. "We have been working on this for so many years — offering good day care, for example — but we still see this. It makes it even more strange and provocative."