What Is the National Best Bid and Offer (NBBO)?
Let me explain the National Best Bid and Offer, or NBBO, directly to you. It's a quote that pulls together the highest bid price and the lowest ask price for a security from every exchange or trading venue out there. What this means is the NBBO gives you the narrowest possible bid-ask spread for that security.
Under the SEC's Regulation NMS, brokers must execute trades at the best available bid and ask prices when handling securities for you, their customer. They have to guarantee you at least the NBBO price at the moment the trade happens.
Key Takeaways
You should know that the NBBO displays the lowest ask and highest bid prices available to you from various exchanges. Regulation NMS from the SEC mandates that brokers provide at least this NBBO price to customers during trades. It's all calculated and shared by Security Information Processors, or SIPs. While it aims to give everyone the best execution prices, remember that NBBO data isn't always the freshest, which can lead to trades not meeting your price expectations.
Understanding the National Best Bid and Offer (NBBO)
Diving deeper, the NBBO gets calculated and distributed by SIPs under the National Market System Plan, which handles security price processing. There are two main SIPs: the Consolidated Quotation System (CQS) covers NBBO for NYSE, NY-ARCA, and NY-MKT listed securities, while the Unlisted Trading Privileges (UTP) Quote Data Feed handles Nasdaq-listed ones.
Throughout the trading day, the NBBO updates with the highest and lowest offers for a security from all exchanges and market makers. The lowest ask and highest bid don't have to come from the same place—that single-venue version is just called the 'best bid and offer,' not the NBBO. Keep in mind that dark pools and alternative trading systems might not show up here due to their opacity.
If you're a trader looking to handle larger orders than what's in the NBBO, check the exchange's depth of market data or Level II screens. Those will show you additional bid and ask prices to fill your order.
Advantages and Disadvantages of the NBBO
On the plus side, the NBBO makes sure you, as an investor, get the best price when trading through your broker. You don't have to hunt down quotes from multiple exchanges or market makers yourself. This evens things out for retail traders like you who might not have the tools to chase the best deals across venues.
But there's a downside: the NBBO might not have the most current data, so you could end up with executed trades at prices that don't match what you expected. This is especially problematic for high-frequency traders who depend on tiny price shifts in large volumes to profit.
Enforcing Regulation NMS is tough because trading moves so fast and NBBO prices aren't always recorded. That makes it hard for you to prove if you got the NBBO price on a trade. Also, prices can be outdated, and not everything shows up—dark pools and alternative systems often don't list their bids and asks.
NBBO and High-Frequency Trading (HFT)
High-frequency traders build special setups to connect directly to exchanges and process orders quicker than regular brokerages. They skip relying on SIP data for bids and offers, instead exploiting the delay between NBBO calculation and its release to make money. Studies have looked into whether this lets them front-run other traders.
A 2013 study from the University of Michigan found that traders could profit up to $21 billion from this latency. As the authors put it, by predicting the future NBBO, an HFT algorithm grabs cross-market differences before they're public, jumping ahead of orders for a small but guaranteed profit. This sparks an arms race where even faster traders predict further ahead.
Example of the NBBO
Let's walk through an example. Say a broker has these sell offers for ABC stock: 200 shares at $1,000, 300 at $1,500, 100 at $1,800, and 350 at $1,600. At the same time, bid prices are: 100 shares at $900, 200 at $800, and 150 at $950.
The NBBO for ABC would be $950/$1,000, as those are the best bid and offer available in that set.
