In one sense you both are right. When a portfolio manager puts in a large block trade, its been common for a long time for execution management systems to optimally handle the execution, by breaking the trade into smaller pieces of varying size, at various prices over a period of time, to try to get the best execution possible. Proprietary systems have been built which are very good at that. So while the gross holdings of a fund might be set by a human, the executions likely are handled by software.
Having worked on an Equity Derivatives desk for a time, I can tell you much of the exchanges' trade volume--as early as 1990--was from DOT (program trading) and super-DOT executions. Monthly volume leaders included Susquehanna Partners, who did almost all of it's transactions via computer (DOT) trades. Late 90s and early 2000s saw the rise of the Swaps market where one deal could generate literally tens of thousands of transactions. It wasn't Bud Fox with a Quotron and a phone doing those executions.
1) Buy-side and sell-side are completely different beasts.
2) Even today, bonds are traded OTC and mostly by people. In the 1990's, 100% of bonds were traded by people. Bond market cap dwarfs equity market cap.
3) Exotic OTC options were a big thing in the 80s and 90s. While that's not true today, when they existed, all of those were traded by people as well.
4) Most hedge funds today manage their positions with excel and trade based on analyst recommendations. They might have some fancy factor ops engine or something, but it's basically an after thought.
5) Around the dotcom boom, Goldman's equity desk had over 500 traders.
Fundamentally we are talking about a lot of different things. Different asset classes, buy-side vs sell-side, NYSE systems vs pit traders, etc etc. We can slice and dice these numbers in many different ways: total number of discretionary firms vs quant, trade volume vs assets, buy-side vs sell-side, etc etc. There's many ways to look at it that result in different conclusions. All I'm saying is that computerized trading is probably not yet the dominant paradigm and it certainly wasn't the dominant paradigm in 2007, much less 1990.
Sure there were high-touch traders, they were still employed up to and around 2017-2018. Since the early 201x's bonuses have been pared to fractions of what they were and each month, every bulge bracket bank lets some formerly well-paid traders go. Fixed income notwithstanding, it's been a tough road for those guys since 2007, have you been to the floor of a major exchange lately? It's lonely. Gone are all those seven-figure a year specialists. No, low-latency and HFT are the dominant paradigm, they are business today. Want more change? Downtown Manhattan used to be all financial. Every block had dozens of Wall St. firms, trading houses, research organizations, etc. Today, it's residential. It's lots of city, state and Federal Government offices. The legions of well-dressed yuppies rushing to get to the trading floor by 7:30 AM... they're gone. Perhaps your experience is different, but this is the reality.
