Exchanges and brokerages from first principles
The global financial system exists to price, transfer, and distribute risk. Every asset (stocks, bonds, derivatives, etc.) encodes a unique risk profile and payoff function, allowing market participants to express viewpoints.
A market is a place where people can go to trade various assets. In finance terms, markets are where buyers and sellers meet to trade assets at prices they both accept. Functioning markets match people who want something with people who have it and determine what price clears the market. Today, almost all financial assets are traded electronically.
Modern financial markets facilitate the trading of assets through order books. Order books are digital ledgers that track all pending buy and sell orders based on price-time priority. Price-time priority dictates that trades are matched based on the best available price, and if multiple orders have the same price, the earliest order by time takes priority.
Order books have bids and asks. Buy orders (bids) stack up on one side, ordered from highest to lowest price. Sell orders (asks) line up on the other, from lowest to highest. When a bid meets or exceeds an ask, the matching engine executes a trade automatically. This process repeats millions of times per day, constantly discovering the price where supply meets demand.
In the US, the market infrastructure is split into two key players: exchanges and brokerages.
Exchanges are venues that define market structure rules to facilitate the buying and selling of an asset. Trades typically occur on an order book on a server. Notable exchanges include NYSE, Nasdaq, and ICE.
Brokerages are entities that connect users to exchanges. Users submit trades to brokerages who execute trades on your behalf through exchanges.
The separation between exchanges (execution venues) and brokerages (order-originators) was the direct effect of the Securities Exchange Act of 1934. Some countries implement a similar bifurcation (Canada, United Kingdom, Australia), while others operate exchanges and brokerages as a unified entity (China, Hong Kong, Singapore).
The vast majority of crypto exchanges operate both the exchange and the brokerage, including prediction market venues such as Polymarket and Kalshi.
This post explores the primary revenue sources of exchanges and brokerages.