That is the preliminary finding of research by Erika Sandow at Umea University. It is based on an inventory of data from 2 million Swedes between 1995 to 2000.
Sandow discusses the limitations of her study in an interview with The Local, a Swedish publication. "There could be another selection process at work there as well, that the 'weaker' relationships can't take that kind of strain in the first place," she says.
Slate Magazine columnist, Annie Low, speculates: "Perhaps long-distance commuters tend to be poorer or less educated, both conditions that make divorce more common. Perhaps long transit times exacerbate corrosive marital inequalities, with one partner overburdened by child care and the other overburdened by work."
Thanks to Jeff Jamawat