This wouldn't be informative as to the effects of fluoride, because the results would be confounded to hell and back. Just to give the most obvious example, the

This wouldn't be informative as to the effects of fluoride, because the results would be confounded to hell and back. Just to give the most obvious example, the states that go for this are going to be the ones where the legislature is more skeptical of government interventions to improve public health, and that's going to affect outcomes in a lot of ways that have nothing to do with fluoride.