You can get even more granular than that. CDC maintains a list of water systems and whether or not they add fluoride. CDC My Water System. To give you an idea of how granular that is, there are 78 different water systems in my county alone. For most of my life I assumed we had fluoridated water but apparently only 1/78 of our water systems are. I only checked when we had kids and I needed to know whether or not I needed to give them Fluoride Drops.
We probably have enough A/B data now to make some inferences yeah? Compare countries with fluoridated water to countries without.
You can get even more granular than that. CDC maintains a list of water systems and whether or not they add fluoride. CDC My Water System. To give you an idea of how granular that is, there are 78 different water systems in my county alone. For most of my life I assumed we had fluoridated water but apparently only 1/78 of our water systems are. I only checked when we had kids and I needed to know whether or not I needed to give them Fluoride Drops.
yes and some of that data is already in other comments here