Duration: 5:57
Level: Beginner

This lesson covers U.S. stock exchanges, alternative trading systems, and internalization.

Contributed By: IEX

Study Notes:

Thanks for coming back for lesson two in our course on equity market structure. In our last lesson, we talked about the US equity markets rule book and regulators the laws, regulations, and regulators that govern the broad structures for trading.

Today, we’re talking about the exchanges and other trading venues. These entities, which are for-profit entities in the U.S., play two roles. Trading venues act as the playing field and referees for trading. They have rules and technology that set up the basic boundaries for how they will match buyers and sellers. Their playing fields must be set up within the confines of the Exchange Act, but beyond that they have some leeway with how trading works on their particular exchange.

For instance, IEX is known for its speed bump, a coil of cable that delays all messages coming in and out of the exchange by 350 microseconds. Trading venues are also responsible for monitoring trading on their venue for   among other things potentially manipulative activity.

So, who are these entities that have so much power over how trading happens?

Stock exchanges: Three exchange families plus IEX

Stock exchanges are the main places where trading gets done. As of the recording of this lesson, there are 13 stock exchanges in the U.S., but that number makes it sound more complicated than it is. There are actually only four stock exchange operators currently in the market.

The New York Stock Exchange was the first U.S. equities exchange. It still exists today and is often called NYSE Classic as a shorthand. It’s the exchange that lists companies like GE and DuPont, but NYSE also owns four other stock exchanges – NYSE Arca, which mainly lists ETFs, and three small, less than one percent market share exchanges – NYSE Chicago, the former Chicago Stock Exchange, NYSE American, the former American Stock Exchange, and NYSE National, the former Cincinnati Stock Exchange.

Next, there’s Nasdaq, which was founded in the 1970s as the first fully electronic stock market and became an exchange in 2006 ahead of regulation NMS, which we discussed in the previous lesson. Nasdaq’s main exchange, just called Nasdaq, currently handles the most trading of any exchange and lists companies like Microsoft and Apple. Nasdaq also operates two other smaller exchanges – Nasdaq BX, the former Boston Stock Exchange, and Nasdaq PSX, the former Philadelphia Stock Exchange.

Then there’s Cboe global markets, the company that bought Bats global markets. Bats was founded in 2005 and started two exchanges, and in 2014 merged with Direct Edge, which also had two exchanges. Those four exchanges, which are part of Cboe, are now called Cboe BYX, Cboe BZX, Cboe EDGA, and Cboe EDGX.

And finally, there’s us, the Investors Exchange or IEX. IEX became an exchange in 2016. It is most well-known for the speed bump mentioned previously, which is designed to help the exchange make sure it has the most up-to-date prices from around the market before executing trades. IEX has also introduced other technology and business practices that are designed to level the playing field for all participants.

All the stock exchanges have applied for and received permission from the SEC to be what is called nationally registered stock exchanges. In this capacity, they’re considered to be self-regulatory organizations or SROs that have significant power to enforce the rules of their exchanges as referees. However, with that power comes a large amount of scrutiny and regulatory oversight, which aims to ensure that the exchanges are operating with a high degree of integrity, security, and precision.

In addition to these exchanges, there are a number of other companies that may be launching exchanges in the near future, including the Long-Term Stock Exchange, the Members Exchange, and MIAX, which is known for operating multiple options exchanges. It’s a constantly evolving landscape and one that you can follow in the news on a regular basis.

Alternative Trading Systems a.k.a Dark pools

In addition to the stock exchanges, trading also occurs on Alternative Trading Systems (ATSs), which are often known as dark pools. They have the same fundamental rules but have some critical differences. These venues can be thought of as more lightly regulated marketplaces for trading. They are often run by large banks. For instance, two of the largest are run by UBS and Morgan Stanley. However, some are run independently such as Liquidnet.

ATSs are called dark pools because in many cases they only offer non-displayed trading, which means that buyers and sellers don’t post out loud or advertise the prices at which they would be willing to trade. Instead, they submit their orders to the dark pool and wait for another order to match with them. Non-displayed trading is also available in exchanges but tends to be more prevalent on ATSs.

Starting soon, dark pools will have to disclose the rules of how trading works on their venues publicly via a Form ATS-N. This is important because the way dark pools operate is more flexible than on exchanges. For example, they can charge more for trading than exchanges. Additionally, after trades occur on dark pools they’re only reported publicly as occurring off exchange and not attributed to the specific dark pool where they occurred.


Finally, trades can also be executed inside large brokerages, for example, by matching or internalizing two customers’ orders. Because large banks often work with a lot of clients and a lot of different departments internally, they sometimes are handling one order to buy and one order to sell of the same stock. Through internalization, they can just match those orders with one another themselves rather than sending the order to an exchange or dark pool.

Brokers like to do this because they get two orders done immediately without sharing any information with the broader market, and they don’t have to pay another entity to execute the order.

Additionally, some brokers also send orders to market making firms, also known as wholesalers, which trade against the orders for their own accounts. This process is also referred to as internalization.

In the next lesson, we’ll talk about what is actually traded in the U.S. equity markets – stops.

Note that videos were recorded in December 2019.

“IEX and Interactive Brokers undertake no duty to update the information contained herein, and the information is provided for informational and educational purposes only.”

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