This past weekend, a friend mentioned that if San Francisco had the population density of Manhattan, it would have a population of 3.3 million, far more than its actual population of 825,000. And I calculated that if San Francisco had the population density of the five boroughs of New York city, including relatively low-density outer boroughs like Staten Island and Queens, it would have a population of 1.2 million. Despite San Francisco’s reputation as a hotbed of progressivism, the city is in many respects very “conservative,” which is to say resistant to change.