Are men more likely to cheat if working with more women, or do cheating men prefer to work with more women?

I recently read this 2013 paper by Masanori Kuroki (Occidental College), published in the journal Economics Letters (sorry I don't see an ungated version anywhere). In the paper, Kuroki looks at whether the sex ratio in the workplace affects the likelihood of marital infidelity for men and for women. She used data from the 1998 General Social Survey (as an aside, you can get the data for yourself here - not just for 1998 but for every wave of the survey, which is a pretty cool resource).

Her measure of the sex ratio of the workplace is based on a self-reported measure in response to this question:

"Are the people who work at this location mostly men or women?" Individuals respond on a 7-point scale: (1) all women, (2) almost all women (e.g. 95%), (3) mostly women (e.g. 70%), (4) about half men and half women, (5) mostly men (e.g. 70%), (6) almost all men (e.g. 95%), and (7) all men.

She then converted the categorical measure to a numerical measure (which just screams out "measurement error", but we'll put that to one side as there is a more important issue with the paper). Her measure of marital infidelity is based on this question:

"Have you ever had sex with someone other than your husband or wife while you were married?"

I'm sure you can immediately see a problem here. The interpretation of the results is not straightforward, since the cross-sectional correlation that results from her analysis will be between current workplace sex ratio and whether the person has ever been unfaithful. Here's what Kuroki finds:

An increase in one standard deviation in a fraction of coworkers of the opposite sex is predicted to increase the likelihood of an extramarital affair by 2.9 percentage points. Considering that 22% of people have committed infidelity in the sample, this magnitude is not trivial...

Next I run separate regressions for men and women... The coefficient on the fraction of coworkers of the opposite sex continues to be positive and statistically significant for men but not for women. An increase in one standard deviation in a fraction of female coworkers is predicted to increase the likelihood of an extramarital affair by 4.6 percentage points for men. 

The coefficient may imply a result that is not trivial, but it is correlation not causation, and as noted above the interpretation is not straightforward. Does it mean that men are more likely to be unfaithful if their current workplace has a high proportion of women, or that men who have a history of infidelity are more likely to choose to work in a workplace with a high proportion of women? The answer is not clear.