"Where would you fit more millions of people in downtown San Francisco?" What has led you to believe this is a difficult problem? The impediments to density in

"Where would you fit more millions of people in downtown San Francisco?" What has led you to believe this is a difficult problem? The impediments to density in San Francisco are regulatory. At Brooklyn's density the city would have 1.6 million people. At Paris's density? 2.5 million. I deliberately chose those places because they're not dominated by skyscrapers. People talk about the "housing crisis" using the language of natural disasters. But this is just people deciding not to build more housing. No more or less.