Huh? Informationless trading is pretty much the exact opposite of algorithmic trading. It has nothing to with volume, it simply means that you are buying/sellin

Huh? Informationless trading is pretty much the exact opposite of algorithmic trading. It has nothing to with volume, it simply means that you are buying/selling not because you have information that leads you to believe the stock in question is about to go up/down but rather because you need cash, or it's an IPO, etc. Algorithmic trading is nothing but informational - the whole purpose is to analyze information, detect a trend, and ride it. Add to that quote stuffing and other price manipulation techniques (emphasis mine). It think it's rather hard to make a case that the robots that make up the majority of trading volume have no effect on prices. I don't know where you get your nebulous is thought not to move prices. Thought by whom? HFT firms and technology providers? Well, duh. They are making a killing in essentially passive income and they are about to get shut down by various regulatory bodies in US and Europe. What do you expect them to say? Of course their party line is, we have a zero net effect on prices, and a positive effect on liquidity.