Zerohedge: This is What Happens When HFT Goes Totally Berserk and Serves Knight Capital with the Bill $KCG

We all know something went horribly wrong in various NYSE-traded stocks today between 9:30 am and 10:15 am. So wrong in fact that the NYSE had to step in and cancel numerous trades in 6 symbols. However it did not DK millions of other trades in 134 other symbols, the vast majority of which we assume traded errantly due to the market making of Knight Capital (as admitted by the company), which today saw its biggest drop ever since going public on volume about 60 times greater than its average. We also all know that one should buy low and sell high. At least that is whathuman traders are taught, and that is what they attempt. Because if one consistently does the opposite, one will simply run out of money. Well, the opposite is precisely what the berserk algo in Knight’s Market Making group may have done if Nanex, which has done a forensic analysis of one of the trades in question, is correct. In other words, instead of at least attempting to provide liquidity via limit trades, Knight’s algorithm acted as a market order… gone horribly wrong. As the third chart below shows what the algo did with furious repetition and steadfast consistency was to buy at the offer, and sell at the bid, in other words buy high and sell low. Over and over and over and over. As Nanex laconically notes, “In the case of EXC, that means losing about 15 cents on every pair of trades. Do that 40 times a second, 2400 times a minute, and you now have a system that’s very efficient at burning money.” Which also means that by not DK’ing several hundred million prints, the NYSE may have just thrown Knight under the bus, because the market maker is suddenly on the hook for tens if not hundreds of millions in inverse market making profits.

Here we will assume that readers are sufficiently familiar with market structure to know that market makers only participate in the market in order to collect liquidity rebates, i.e., to be the limit on the bid which is hit, or the offer which is lifted. What Knight did was effectively the opposite, and it also collected the opposite of a rebate: i.e., it paid someone else for no reason at all… well technically to withdraw liquidity. However liquidity that led to creation of losses not profits.