I checked the paper, an unpublished draft. The sample size of non-marital breakups is 279. Also, the question asked was "who wanted the breakup more" not "who initiated the breakup".

85 breakups were reported as mutual. That leaves only 194 breakups which were reported as wanted more by one side.

112 is the total number of breakups reported as wanted more by the woman. 82 is the number of breakups reported as wanted more by the man.

112/194 = 57.7%. Of a very small sample. With the wrong question asked.

Is this the best data we've got? If so, I am not sure we can conclude anything about breakup initiation outside of marriage.

Link to the paper: http://web.stanford.edu/~mrosenfe/Rosenfeld_gender_of_breaku...

Note: It's not clear to me how the author got 56% and 53.4% as the weighted breakup wanted by women rate. It's possible I've made an error. But the Huffington post headline certainly seems unwarranted.