Portlandia's appearance in first place is unsurprising. We have the dubious distinction of having an urban growth boundary, which limits supply; we live in a neighborhood where housing is absurdly overprices (San Diego, LA, San Jose, San Francisco, Sacramento, Seattle/Tacoma are all in silly price land; we have nice moderate weather with the best summers in the world; and China continues to spew expatriates with loads of money looking for a safe harbor.
All of this means Portland is a good place for many of the high land price refugees to flee to. So, we see our middle class neighborhoods filled with older folks, neighborhoods once filled with kids now filled with oldsters. Depressing.
Look on the bright side, housing markets like Portlandia's always are volatile, we are likely just setting up for the next huge crash! How cool is that?