A related question about police quotas suggests there are quotas (some openly, some not) in some jurisdictions.
This Venture Beat Article strongly suggests that more tickets are issued at the end of each month, as police officers try to meet their quotas.
The data certainly shows a lumpiness. It doesn’t show an average number of tickets issued on each day or in each week. In fact, the date shows more tickets issued near the end of the month — and the beginning of the month.
There's a Hacker News discussion, in which these statistics are challenged
Warning, bad science! Looking at the last plot, you can't conclude that police give out more tickets at the end of the month, unless you also conclude that police like to give out tickets around the 8th, and don't like to give out tickets around the 11th of each month. Problem is, there are no error bars, if there were, it'd probably show that there is no significant evidence for the hypothesis. The error of the mean of the last plot is probably comparable to the signal itself.
Are there higher quality studies to examine this question?