In Lewis' book, he talks about how HFT makes profits at expense of other investors. In particular, when large institutional investors make trades, they tend to suffer excess slippage costs whenever they execute large orders. On an individual transaction, they may lose up to 0.1% of the transaction value to HFT. For a single order, this is not large, but it does add up over many transactions. As a result, the existence of HFT reduces the returns for institutional investors. Retail investors are less impacted because their order sizes are considerable smaller. Retail investors are impacted through the mutual funds or exchange traded funds or pension funds they are invested in. Since these large institutional investors earn lower returns due to HFT, the individuals invested in these funds experience lower returns.