The Private Auctions

In Chapter 25, Larry Harris explains why the stock market isn’t just one big room. It’s actually thousands of little private rooms all trying to steal business from the main floor. This is Market Fragmentation.

Three Ways Your Broker “Hides” Your Order

When you hit “buy” on your app, your order might never reach the New York Stock Exchange. Here’s why:

1. Internalization: Your broker is also a dealer. They see you want to buy 100 shares, and they just sell them to you from their own inventory.
2. Preferencing: Your broker has a “best friend” relationship with a specific dealer (like Citadel or Virtu). They send your order to that dealer instead of the exchange.
3. Crossing: Your broker sees that Client A wants to buy and Client B wants to sell the same stock. They just match them up in-house and keep both commissions.

PFOF: The “Kickback” That Lowers Your Fees

Payment for Order Flow (PFOF) is when a dealer pays a broker to see their orders.

• The Criticism: It looks like a bribe. Why should a dealer pay to see your order?
• The Reality: They pay because retail orders are “easy.” Regular people aren’t insiders. Trading with you is safe and profitable for a dealer.
• The Benefit: In a competitive market, brokers use that PFOF money to lower your commissions to $0. You get free trading because your “uninformed” order is a valuable product for the dealers.

The Standard of “Best Execution”

If your broker is getting paid to send your order to a specific dealer, how do you know you’re getting a good price?

• The NBBO: Dealers are legally required to match the National Best Bid and Offer. If the best price in the whole country is $10.01, they have to give you $10.01 or better.
• Price Improvement: Often, these dealers will actually give you a better price (like $10.009) just to keep the brokers happy.

The Dark Side: Why Fragmentation Hurts

If all the “easy” retail orders are being siphoned off into private rooms, what’s left for the main exchange?

• Toxic Flow: The only orders left on the public exchange are the big, scary, “informed” institutional orders.
• Wider Spreads: Because the public limit order traders are only trading against pros, they widen their spreads to protect themselves.
• Weakened Incentives: If a dealer quotes a great price on the NYSE but all the orders are being internalized anyway, they have no reason to quote that great price.

Summary: A Trade-off for the Small Guy

Internalization and PFOF are a win for the small uninformed trader (who gets zero commissions and fast fills). But they are a loss for the limit order trader and the overall transparency of the market. We are trading a little bit of market efficiency for a lot of convenience.

Next time, we’ll look at Chapter 26 and the war between different market centers.

Next Post: The War Between Market Centers