We have gone beyond gentrification and are now talking about Pikketyfication, aristocratization and plutocratification.

Henry Grabar writes in Slate about The Incredible Shrinking Mailroom, how fewer and fewer people are living in New York apartments, as buildings get renovated and apartments get combined.

"...more than 300 New York buildings are renovated to decrease the number of units each year. They’re concentrated in just a few neighborhoods where developers think there’s demand for bigger, more expensive units—and are adapting properties accordingly."

Census/Public Domain

This is not a new phenomenon; population density in New York and other cities has been dropping for a hundred years, first to gentrification and more recently, Aristocratization, after a famous Onion article. It could be also called Plutocratification or Pikettyfication, where the extremely rich push everyone else out, and turn entire apartment buildings into single family houses. I wrote a few years ago after 9 apartments were converted into one house:

How about recognizing that New York is going through a massive de-densification as the number of people per square foot continues to plummet, because the rich can afford to do this and the occupants in the nine units cannot afford to stay under such conditions.

How about recognizing that the problem here is inequality. That the very rich are getting a whole lot richer, and that the occupants of nine little apartments don't earn enough to stay in their apartments.

That is why successful cities are changing. Jane Jacobs wouldn't recognize her old stomping grounds today; there is no "intricate sidewalk ballet". She wrote about her home in Greenwich Village:

When I get home after work, the ballet is reaching its crescendo. This is the time of roller skates and stilts and tricycles, and games in the lee of the stoop....They slop in puddles, write with chalk, jump rope, roller skate, shoot marbles, trot out their possessions, converse, trade cards, play stoop ball, walk stilts, decorate soap-box scooters, dismember old baby carriages, climb on railings, run up and down.

Not anymore. The kids, if there are any, are inside. Parents wouldn't think of letting kids play in the streets. We actually changed the date of Katherine's post 7 reasons to let kids play in the streets because we were afraid people would think it was an April Fools' joke.

Henry Grabar concludes:

But if there are elements of midcentury urbanism that we do want to recapture—busy sidewalks, vibrant neighborhood social institutions, transit ridership—we have to remember that all those buildings were much more full than they are today. Want a city that functions, at street level, like that one did? Unless you’re adding a kid to every family, you had better build some bigger buildings.

Perhaps. But when those bigger buildings get built, they are rarely affordable, especially in cities like New York or San Francisco. There are rarely eyes on the street, because the ground floors are filled with loading bays and drugstores with blanked out facades. And nobody is going to let their kid ride their tricycles in the street and you get arrested for climbing up railings.