Earlier quoted context omitted.
"Suffice to say, there were/are pros and cons to having a specialist." Let's not go there. Specialists were accused of favoritism: filling orders that certain traders submitted and ignoring requests from other traders. More generally, the advancements, both in technology and in pricing, actually helped everyone. SOES (small order entry system) helped smaller traders to quickly trade. Decimalization really helped redu…
yes and sophisticated HFT systems screw large funds from moving into and out of positions with relative ease/fairness. This cuts both ways, thus pros and cons. At least with a specialist, everyone was relatively even in that regard. Now, measuring the distance to the server in micro-seconds of fiberoptic wires, I can literally create an unfair system by owning the closest supercomputer. I disagree with your point and…
Fact: when you make a large trade, there is a price impact. I.e., if you sell lots of GOOG, the price goes down.
Once upon a time, large funds could use their own sophisticated algorithms to make sure their unsophisticated counterparties feel the price impact. I.e., the big fund disguises their intent, Joe IRA buys from the large fund, and then the price goes down after Joe already owns the stock.
Nowadays, HFT makes the price impact happen immediately, typically splitting the difference with Joe [1].
Why is this worse?
[1] The HFT's try to outbid the large fund in order get ahead of it, resulting in Joe getting a better price.