From memory, one thing that surprised me was holidays. Thefts decrease in the days before a holiday that's basically just a day off for most people, but thefts increase in the days before a holiday that has a strong tradition for getting together with the extended family.
I've always wondering if this was a money issue (ex: how expensive holidays can be), or a stress issue (ex: distracted about the 20 things that need to get done today before the inlaws arrive / deadlines because of employees being out of office)
