in large and growing metro areas, there has been an undersupply of housing. particularly in cities, i know, you know, affordable rental units particularly, but generally, supply has not expanded as much as it should, that pushes up prices. that's a structural issue. but what has happened in the past few months no make this happen now? because it seems to acute, so specific, and so sharp. >> it's not really the past few months. we've been underbuilding, as you showed in your chart, for many years, because after the great housing crash, the subprime mortgage crisis when the builders just got slammed, they pulled back. they didn't want to build anything over than what they thought they could sell. they've been slowly, very slowly, climbing back. you ask the question, if there's so much demand and builders are getting such demand, why aren't they building as many houses as they possibly can? go back to supply issues, labor issues, land issues, material costs. they cannot build the types of