The stat with the house is your base score the higher the score the more people will join. Base score is based on the amount and quality of things in your base. I havent balanced it yet though. Stone and metal buildings are worrh more then wood. Most of everything else is worth 1 (but will change later). Now the max npc population is 8 I probably need to adjust the rate on which people arrive. If you build it they will come.