The author of the piece seems to be taking the tweet about half the journalists under 40 living in that area pretty literally.

I don't know if the author of the tweet intended it that way (and if he was speaking figuratively I wouldn't fault him, it's just a tweet), but I don't quite buy that anyone could really estimate the number of journalists in an area drawn by someone else by eyeballing a map on Twitter. I also don't quite buy that half of the journalists under 40 live in a specific part of New York City, when Washington DC, Los Angeles and (for nerds) San Francisco also have their own share of that population.