The Nordic nations are frequently held up as countries that have come as close to any in creating true gender equality. Case in point, in the World Economic Forum's 2015 Gender Gap Index, an annual ranking that measures the gap between the sexes in health, education, economic opportunity and political representation, the top four spots are taken by four Nordic countries: Iceland, Norway, Finland and Sweden.

And though the remaining Nordic nation, Denmark, languished in the relatively low 14th place, it is worth remembering that was still 14 places higher than the United States.

However, these statistics don't necessarily mean that everything relating to gender within the Nordic countries is perfect. In fact, as a new report points out, the Nordic countries appear to have a disproportionate and perplexing amount of domestic violence, or intimate partner violence (IPV), against women.

Investigating what they refer to as the "Nordic paradox," Enrique Gracia of the University of Valencia and Juan Merlo of the University of Lund write that they found a surprising lack of research on the subject. Their paper, published in the Social Science and Medicine journal, not only examines the problem but also suggests how a better understanding of this paradox could hold crucial lessons about violence against women.

IPV is the most common form of violence against women, and it can be deadly. Globally, 38.6 percent of all women killed die at the hands of their partners, according to a study from the London School of Hygiene and Tropical Medicine. Nordic countries, despite their famed gender equality, stand out on comparative rankings of IPV prevalence. Figures from the European Union Agency for Fundamental Rights, or FRA, show that the three Nordic E.U. member states — Sweden, Finland and Denmark — may experience far more violence directed at female partners than the E.U. average.

A separate study of IPV prevalence in Norway, a non-E.U. member, found a rate of 26.8 percent — also above the E.U. average — while a study of Iceland found that 22 percent of women had experienced domestic abuse. This may come as a surprise. You might well expect better gender equality to mean less violence against women. To add to the intrigue, when you look at European countries with relatively low levels of gender equality — Italy or Greece, for example — they seem to have lower levels of IPV.

One reasonable assumption would be that greater levels of gender equality perhaps lead more women to report violence from their partners, though not necessarily more acts of violence against partners, which may be underreported in less gender-equal countries. This is something that the FRA's report suggests. "Gender equality could lead to higher levels of disclosure about violence against women," the report states. "Incidents of violence against women are more likely to be openly addressed and challenged in societies with greater equality."

Gracia and Merlo consider this possibility but don't seem to find it convincing. They point out that the FRA's report contains data that suggests that, on average, 20 percent of female IPV victims across the E.U. reported more serious crimes against them to police. Meanwhile, only 10 percent did so in Denmark and Finland and 17 percent in Sweden. Instead, the authors reason that another factor may be at play, such as a backlash against women in more gender-equal societies and anger over the relatively high status of women compared with their partners in such societies.

In fact, Gracia and Merlo say, there could be other reasons for IRL that are unrelated to gender equality — similar patterns of alcohol abuse, for example. They urge more research on the matter, so that policies can be designed to "appropriately respond to this social and public health problem in a more effective way."

In all, the report shows that gender equality is often more complicated and sometimes confounding than simple rankings can show. This probably won't surprise those living in Nordic nations: Last year, Cecilia Schelin Seidegard, head of the Swedish government's special inquiry on gender equality, accused her country of resting on its laurels when it came to gender equality, pointing toward continuing violence against women as evidence that Sweden still had far to go.

"There is a long way to go towards an equal society," Seidegard wrote.

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