So where does the human intelligence aspect of trading securities / currency / stocks happen? is it ever done by individuals who have no affiliation to a firm or institution? or are these days over
You're being sidetracked. You asked for "day traders in New York". Heck, maybe you're doing your documentary on the decline in day trading.
Yet, if you don't care if they are trading 5hrs per week, 20hrs per week or 40hrs per week or 60hrs per week...getting caught up about if they're this and that won't accomplish your goal of meeting them unless you're actually looking for a specific type of day trader.
Yet, if you're looking for professional institutional traders that work for financial institutions, you're at the wrong forum. Instead, you're going to need to go to the Universities in the New York area and then get permission from the school to talk to the traders (grad students) using their "trading rooms". As to you talking to an actual institutional trader...the firms won't allow it but maybe if its part of some internship program you're doing.
Yes, there are lots of institutional trading still done by humans and lots of retail day trading still done by humans. Many financial institutions still put out videos online in the past year to show there human traders. They also are now allowing a peak at their "humans" that are monitoring their algorithm trading systems...they looked like a bunch of nerds (quants) that are paid very well.
Darn humans...they're still everywhere. It'll be another 100 - 200 years before all trades are 100% algorithms and you'll need no human intervention. By then, we've have robot cleaning maids, robot restaurant workers and maybe even robot girlfriends.
Like the big hint I gave you earlier. There's a big decline in ALL types of trading and day trading is more spread out now with the rise in social media like twitter and stocktwits. In addition, as explained earlier, there's a current big shift of day traders to Europe and Asia due to the shift from New York into London, Hong Kong, Singapore as the leaders in that type of trading.
I'm just guessing that the shift is due to the shift into the FX markets that's big there.
Now the question for you is this...is there a specific type of day trader you're looking for that lives in New York ???
Thus, you should be very specific about what your documentary is about unless at the moment you don't even know yourself and you will decide upon the subject
after you meet the day traders in New York.