Since you used to be in charge of a public water supply system perhaps you know the answer to this question.
Are large cities more likely to have fluoride added to their water supply when compared with rural areas and small towns?
If so, perhaps adding fluoride to the water causes not just lower IQs but also more violent behavior.
I probably should have added an LOL or a /s to my post.
I’m not really suggesting that correlation is causation - but if you look at our large cities you will find some very low IQs and much violence.
Large cities are probably more likely to fluoridate their water, but most public water supplies probably do, whether in a large city or not.
If you have your own well, your water is almost certainly not fluoridated.