I'm not parent, but here's an idea that's floating around, maybe it can be used as a reasonable guess to as how to make sense of it: There is a concern that hi

I'm not parent, but here's an idea that's floating around, maybe it can be used as a reasonable guess to as how to make sense of it: There is a concern that high frequency trading is technology that, while creating liquidity, increases the tax paid by long term investors. Instead of having a meaningful spread, long term investors often have trouble filling an order before the entire market jumps, settling back down less than a tenth of a second after the investor's trade clears. The tax is paid a different way, and often at much higher amounts, given the limited data coming from trading arms of various banks. So there is more liquidity, which is good (although, as a civilian, I still need 3 days for _my_ trades to clear on the stock market, so I guess if it was such a huge public good for trades to clear faster the rules would be different). But the market is so jumpy, and so few of the orders placed reflections of actual investor intent, that markets can enter free-fall more easily (because it's happened for no reason). So there is higher liquidity, but it doesn't come with two of the upsides of a free-flowing market: stability and lower transaction costs.