Note from the editor: This column, linked below, pinpoints local governments as the cause of “unaffordable housing.” Briefly: Local governments restrict new housing, which limits the supply and pushes rents and prices up. In the San Francisco area, new housing is prevented in order to preserve open space. Here in the Boston area, new housing is prevented by numerous zoning restrictions: no new housing in basements, attics, or backyards, no subdivision of large units into smaller ones, no easing of parking space requirements, etc. Note how extreme San Francisco area rents and prices are compared to Boston area, where rent and price increases are easing up because of new construction coming on line. The answer to cries for rent control: allowing more new housing.