I am trying to keep my town at 8, deliberately. I have had to hand feed them to get this to happen. I grew exactly 8 veggies thinking it would not be enough for a new resident, but one moved in anyway. When I get it back down to 8 I will try selling exactly 8 apples to the store (I have them in cold storage in the basement of the Mayor's house) and see if that works. Eventually I will need to fill the town as this population manipulation takes a lot of effort.