Market Structure News SEC Announces Roundtable on Trade-Through Prohibitions Will be lots o' fireworks. I am mixed. In theory they shouldn't need an order protection rule (OPR), why trade at a worse px if a better price is there. Conversely..., 1/x

2/x, OPR forces exchanges into same matching model (price time), forces brokers to connect with all exchanges (creates fragmentation), and buy data from all exchanges. Getting rid of OPR should allow a more robust block market, more speedbumps, alternative matching modes...

and allow exchanges to be more creative. But small exchanges will get killed and it will be harder to ensure retail doesn't get overlooked. Retail will complain, exchanges will complain, start up exchanges w/complain (except those w/novel model). Inst brokers & buyside happy.

@daveweisberger1 if deminis, w/b ok for most except large exchange groups w/many small venues. Not sure retail brokers will cry too much if that happens. Also if OPR dies - spreads will probably widen. But most market don't have OPR & Europe has tighter spreads than US. But Euro is different.