There are also only nine possible boost combinations in the game, even though with nine province types, there could be many more, so there should only be nine possible answers to this. But I do not think anyone has ever done the very tedious work of counting it out. And yes, it varies a bit. In my smaller Beta server city, I counted mine up after completing the 130 needed to get into chapter 7, and of the nine types, I had amounts ranging from 12 to 17 of each.
Edit: I just finished completing the last of the Ring 8 provinces, giving me a total of 144. Divide that by 9 and you would have 16, but because of the way the provinces are distributed on the map, I have a range of between 14 and 18 for each type.