Marginal Revolution: High-frequency trading
I’m not a believer in the strong versions of efficient markets hypotheses, so I do admit that high-frequency trading, like just about every other trading strategy, can bring short-run “whiplash” effects on market prices. But if you don’t like it, you can trade yourself at much lower frequencies, which is probably what you should be doing anyway. At the same time high-frequency trading smooths out or shortens many other cases of price whiplash. High-frequency trading brings more liquidity into the market. Call it “low quality liquidity” if you wish, but it still looks like net liquidity to me.