First off remember that there are two options if it's going out from IB - the payment for order flow (which IB may match internally or route to dealer/MM) or exchange. So as MM to get IB order you're already adverse selected on one hurdle (IB didn't match internal), rest of street could've seen it (and may have passed on it), and I'm now holding it. And, IB lot that id see as a dealer is probably someone like you - not HFT ping pong. I need to look at 505/506 data - I can send you a chart pack when I dig it up - but my modeling of markups/PFoF used IB as the proxy/control versus dumb money retail, it's basically the opposite of robinhood flow all things considered, and partially because of their model. As a MM, I'm going to have some buckets of predictable flow: - Money manager type accounts who are one-way in a name; VWAP/TWAP orders, perhaps, or I'm talking to them and I know - Option-driven, index-driven (which is the offset, here AP create-redeem more important) - Much of what is thematic / the herd is one directional - Pods, which all herd and I'm basically playing a momentum game against them and waiting for their blow ups to monetize, but which I can predict - if pod A is buyer at 11am, pod B will be at 11:15 (esp if they have any momentum-type pricing - usually it's clusters of them coming in off each other, it is very amusing in practice) An IB order is the most likely to be informed, yes - because it has broad retail access AND funds can route through it. If I'm at a large dealer, they're a broker. They're not a client. They have a sales rep, probably, but I'm going to treat them as an adversary, the brokers still pick you off. The client did not route to me - I do not get (necessarily) a promise of a future trade or relationship benefits - nor do I have a sales guy who has an idea of why you're executing. Bursty random flow - even if "unintelligent" - can still be quite toxic, as well. If one of my clients is doing a large trade - and large in market impact - and he says he's done, then he goes sells more on another venue, that's toxic/unpredictable, hurts my ability to hedge/distribute. And a routing from a broker is max adverse selection because IB will just route across street as treated the same. So also scenario where if I'm not axed and getting hit by a broker, I'm going to widen out, usually you look into that & assume something went wrong, you were quoting poorly, there was some arb (again, broadly but maybe less the case in cash equities - brokers are actually the worse for dealers - because, here I'm talking less liquid markets/derivs/swaps experience, many of them pick you off when your quoting is off/look for arbs, because there's no trust relationship). So if you were sending in your order, I may see this 50k lot from IB, but if it was my client, I may be able to have them TWAP/VWAP it and that is what makes it predictable. Basically intraday 15 minute reset TWAP/VWAP - distance from here is "is MM pissed off", to simplify. I worked for one of the large dealers and sat by the algo sales traders on the equity side + covered some large etrading accounts on the treasury side.