"You're all committin' suicide!"
--Lewis Zabel (Wall Street: Money Never Sleeps)
Interesting then-and-now of the UBS trading floor in Stamford CT. Pre-financial crisis in 2008 when it was one of the largest trading floors in the world:
Of course, perhaps some capacity has merely been shifted elsewhere. More probably, trading capacity has been retired due to overbuilding during previous cycles.
Plus, increasing share of daily trading volume on many exchanges is being executed by robots.