macrocephalopod

I think shaping our market structure around optimal outcomes for active day traders and internalizers, rather than mutual funds and pension plans, is a mistake. And marketing wirehouse traders as "retail" / "mom and pop" is just that - marketing.

px improvement even greater for institutions/large funds!

Serious question: can you document these price improvements? I am curious how this works in US equities. As you know I come from a largely OTC market....

what do you mean document? recently one firm released earnings saying they delivered over 1 billion in px improvement.

Document means to provide evidence, not make a simple assertion. Provide the tick data and the trades that *show* it.

i would never betray my clients trust by posting their order flow

I am pro hft in general but there is definitely an argument that most of the px improvement that retail sees is not ‘real’ — in the sense that by moving retail flow off exchange, you leave the more toxic flow (from prop shops, hedge funds etc) behind, so exchange market makers...

need to post wider spreads. Since px improvement is measured against exchange quotes, it is mechanically an ‘improvement’ because its being measured against a price that has been made worse by the very fact of moving the retail flow off exchange.