Zoning rules decide what may be built where, and they are among the least visible and most consequential decisions a local government makes. A rule requiring a minimum lot size sounds like a technical matter of land use. In practice it sets a floor under the price of housing in that area, because a house on a large lot cannot be cheap. Rules requiring parking spaces, or forbidding buildings above a certain height, work the same way. None of this is hidden, but it is written in a form few residents read, and its effects arrive years after the meeting at which it was decided.