> Be clear what you are saying. They are "manipulating the price at other exchanges" by changing the prices they themselves set on their own inventory. Which w

> Be clear what you are saying. They are "manipulating the price at other exchanges" by changing the prices they themselves set on their own inventory. Which will be sold instantly, as they have 'discovered' the price on the other exchanges were lower than where the initial order went to, bought that, and then instantly, give or take a few milliseconds, resell. It is not price discovery, it is price manipulation. HFTs have no inventory, they are perfectly lean, they throw hot potatoes across different exchanges. Not that this is not interesting technology. It is, but it is also manipulative. I exclude prop trading from the above, obviously, because it is different, and does hold inventory.