The time of the month to take a sick day

Tyler Cowen prudently refrains from opening comments on his post linking to a paper that deals with the impact of menstruation on the gender gap in wages. I found the data set in the first paper interesting. Is an Italian bank really representative of the working population? How might differences in preferred contraception methods affect absenteeism (birth control pills lead to lighter periods for many, as the researchers noted, but they have their own side effects; IUDs are common in many parts of Europe and can lead to heavier, more painful cycles)? Thoughts?

All this reminds me of a Connie Willis story about the coming Liberation.