He says "single ledger" which I think alludes to the NBBO rule in a normal stock sale. Brokers are required to guarantee that customers get best prices while bu

He says "single ledger" which I think alludes to the NBBO rule in a normal stock sale. Brokers are required to guarantee that customers get best prices while buying/selling. So they aggregate prices from all the exchanges, at least in US, and present it to the customers. When the trades are placed while they might be routed to exchanges for execution but they are effectively working as a single market. Bitcoin volatility has lot of problems, a lot of them due to market micro-structure. There is also no dedicated market maker because the risk in bitcoin deal making would be huge.