Nate Silver's fivethrityeight published an article with research on injuries that required time off work provided by the Bureau of Labor Statistics. Interestingly, the research shows that Mondays are the worst days for incurring injuries. Like good data compilers, it does consider that there are more holidays on Mondays and people are likely to take Monday off from the work week to make a long weekend and that maybe those reasons add more injuries to Mondays at a higher rate than other days of the week.
What the article does not discuss is that Fridays produce the fewest injuries. Isn't that the day the excuses for injuries at work could seem highest? Like, employees are most excited for the weekend on Friday and maybe least focussed? And, Fridays are not the "safest" day by only a small margin; Fridays are the safest by a considerable gap.