Another one is high-frequency trading, where different firms (only the top dogs can afford this) pay to put their servers/systems closer to the central NAS or other exchanges' geographical locations, so their hardware/software gets trades and info a few milliseconds before others and carries out executions with a high advantage. There are some good articles on this if you google high freq. trading, reading through it I don't see any way its not illegal to get an edge before any trading actually happens.
Not that anyone had an illusion we were on a level playing field with UBS, Goldman etc )
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