Fundamentally the biggest reason to have a hub and the biggest barrier to creating a new one is coordination. Existing hubs are valuable because a lot of the coordination work is done FOR you. People who are effective, smart, and wealthy are already sorted into living in places like NYC and SF for lots of other reasons. You don't have to directly convince or incentivize these people to live there for EA. This is very similar to why MIRI theoretically benefits from being in the Bay Area: They don't have to pay the insanely high a cost to attract people to their area at all, vs to attract them to hang out with and work with MIRI as opposed to google or whoever. I think it's highly unlikely that even for the kind of people who are into EA that they could make a new place sufficiently attractive to potential EAs to climb over the mountains of non-coordinated reasons people have to live in existing hubs.
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