Philadelphia couples who have never been married were more likely to be involved in domestic violence calls than others who had tied the knot, according to a new statistical analysis of a whole year’s worth of police data in Pennsylvania’s largest city.

Some 82 percent of intimate partner violence incidents were between dating partners—with the remainder involving those who were married or previously married, report the scientists from the University of Pennsylvania in the journal Preventive Medicine.

Though there are limitations to the conclusions, the data appear to indicate that more domestic violence happens with people dating, as opposed to those who have taken the vows.

“Current boyfriends or girlfriends were more likely that current spouses to injure their victims and to be arrested,” they conclude.

The 31,206 incidents were catalogued by Susan B. Sorenson and a colleague at Penn, amid the 2013 DV data provided by the Philadelphia Police Department.

Of the 82 percent portion of the domestic violence incidents attributed to dating partners, it was split between currently dating (44 percent) and formerly dating (38 percent) partners, according to the data.

The remaining incidents involved spouses. Current spouses made up a total of 15 percent of the calls, and 3.5 percent involved ex-spouses.

But there are limitations and confounding factors. For instance, Philadelphia has the highest percentage of never-married adults (51.5 percent) among the 10 biggest U.S. cities. Underlying that statistic is a changing nature of relationships over the period of 1970 to 2009: over that time frame the median age of first marriage for men rose from 22 to 28, and from 20 to 25 for females. (Divorce rates also doubled over that period.)