>No it's not, since with the houses it would be easy to verify that there's no 3 houses available. The trader in the Nanex article had no way to know how many o

>No it's not, since with the houses it would be easy to verify that there's no 3 houses available. The trader in the Nanex article had no way to know how many of the 24800 shares were actually available. He's trading at an information disadvantage. You are correct, public markets are anonymous by design, so there is no way to tell that the same liquidity is being offered in more than one place. That doesn't change the reality that it is. As I explained, it must be, or the transition from 1 exchange to 13 exchanges would have seen offered liquidity by market makers cut to 1/13th. So like I said, anyone with a working mental model of the market knows this. You can't just aggregate displayed liquidity at each venue and think that number is valid. It doesn't matter what your 'screen' is telling you if the screen is doing something that makes no sense. No one ever pretended that you can magically execute on different exchanges as if they were one exchange. No one ever made that guarantee. The only people who think that are wingnuts like Eric. And since we are talking about an issue that only effects people sending very large orders to multiple exchanges, the likes of Katsuyama have no excuses for their ignorance. They are paid to be on top of these details. You can't have a 'trader' in the modern age who doesn't know what a millisecond is, or isn't prepared or capable to dig below one abstraction layer. "dUh, my screen say 24800 shares are there and i pressed buy" is not what you pay an execution trader for. It is his fucking job to know what happens when his order goes down the wire. >To your analogy, it would be similar to a real estate agent flooding the market with multiple listings of each house, but with different pictures and different addresses, giving the impression of a buyers market to a buyer (phantom liquidity). They are not "flooding the market" or trying to present "phantom liquidity". They are doing exactly what you do when you put the house on 3 different websites. Trying to increase your chances of finding a customer. They are forced to put bids and offers on 13 different exchanges, because that is US equity market structure. It's no fun. Life would be a lot simpler if there were just one exchange. As I explained, it's like playing russian roulette for them... they are now forced to take the chance that they may get filled simultaneously on multiple exchanges and take on more risk than they are comfortable holding. But they are forced to do that since their customers are now spread across 13 exchanges. Market makers would like nothing better than to have 1 exchange. Arbitrageurs are the ones who love having all this fragmentation.