Even if the automatic trading becomes a majority of the traded volume, the impact of human trading might still be higher. That is, it could be that most of auto

Even if the automatic trading becomes a majority of the traded volume, the impact of human trading might still be higher. That is, it could be that most of automatic trading doesn't move the price much in average, while human trades make the price jump more (in reaction to news, mergers, etc). Human trading can only be eliminated if someone develops strong AI. Besides, a lot of what is called algorithmic trading is driven by human, "manual" decisions: say a fund manager wants to buy $10 million worth of stocks someone composing the S&P 500 today, without raising the price of ACME too much, so they use a piece of software that does that automatically.