A second numerical rule is the "Five Excitements" rule, which says that, for each of the neighborhoods, there must be a bare absolute minimum of five reasons I'd be personally excited about PCs visiting there. This one isn't like the 1/8th in that it's not also a target; it's just a ground floor that I'm happy to exceed by as much as possible. Mainly it's to remind myself that even the smallest neighborhood needs to deserve its pages or else be made to sit in the corner until it apologizes.