&gt;I don&#x27;t understand how anyone can say with a straight face that adding more housing exacerbates the problem of not having enough housing.<p>Say you have a building with 3 units all of a type that do not appeal to foreign investors and wealthy people looking for pied-a-terres, and thus are occupied by people who live and perhaps work in San Francisco.   Tear it down and replace it with a building with 10 units, all of which do appeal to the aforementioned investors and wealthy people. Then say 8 units get sold to investors who leave the units unoccupied most of the time, and 2 units get sold to people who want to live in the neighborhood. You&#x27;ve now reduced the amount of housing stock available to San Franciscans, even though you&#x27;ve increased the total number of units.<p>We&#x27;ve had discussions here on HN relatively recently where people discuss housing price inflation in London caused by foreign investors. Vancouver also has a large number of condo high-rises that sit mostly empty most of the time, because they&#x27;re not occupied.<p>That can just as easily happen in San Francisco.<p>Obviously that won&#x27;t happen if we build 10 million units. But we&#x27;re not going to build 10 million units. The danger is that San Francisco builds enough units to attract additional investor demand, but not enough to satiate that demand. Which could leave actual San Franciscans worse off.