Market-order routing across linked venues

A listing is a destination problem

Shares of a company listed on one primary-listing can also trade on regional exchanges and electronic communication networks, sometimes at different displayed bids. Order-routing is the choice of which listing venue, regional book, or electronic communication network will receive a live order.

A market-order is an instruction to trade immediately at the price the chosen destination will give, which can differ if the same size is sent to more than one book. Sending the same sale as a market-order to several venues can result in several different fill prices.

The primary-listing as reference

Venues displaying the same listing are electronically linked, which limits how lasting a cross-venue price gap can be. When venues disagree, the listing or primary-market price is the reference to rely on. The primary-listing is the exchange where the company is officially listed and whose quote is that reference.

Equity market value is outstanding share count times the current price and does not depend on which exchange last traded the shares.

What the tape and give-up leave out

Exchanges do not publish a daily recap of which members or market makers bought and sold, and such a recap would still mix customer-agency flow with proprietary activity.

The tape is the public record of printed fills, which may omit a firm’s own completed orders. Tape prints of public fills do not necessarily disclose a firm’s own filled orders.

A give-up is a member-firm identifier attached to a handled trade, which does not by itself reveal that firm’s inventory or intent. Member give-up identifiers can be obtained, but those labels alone do not reveal useful net positioning.

Two traders can take different live actions in the same situation, so tracking others in order to copy their methods is not a workable approach.

Paper-trading and live size

Actual orders change the market; a paper-trading simulation does not produce that feedback. Paper-trading is a simulation of entries and exits that does not send size into the book and therefore cannot show how a live order changes available prices.