Prior to now few weeks, we’ve got proven knowledge on the expansion of darkish buying and selling and the growing fragmentation of lit exchanges. Right now, there are 16 fairness exchanges, over 30 ATS venues, and greater than 100 brokers within the U.S. — they usually’re all competing to offer buying and selling companies.
That appears like loads of fragmentation available in the market, which sooner or later would possibly lead to extra prices than advantages to traders.
Right now, we’re going to make use of the identical take a look at the U.S. Division of Justice (DOJ) makes use of for mergers. That take a look at exhibits that the U.S. inventory market is, already, extremely aggressive.
The DOJ makes use of HHI as a measure of competitors
The DOJ makes use of the Herfindahl-Hirschman Index (HHI) when contemplating the antitrust implications of mergers and acquisitions. The HHI, based mostly on the work of economists Albert Hirschman and Orris Herfindahl, makes use of the market share of all of the corporations in an business to measure how concentrated it’s.
In easy phrases, the HHI index is created utilizing the weights of every firm in an business. To do that:
- Every firm’s market share is squared (this makes bigger firms depend far more).
- Then, the scores are all summed up.
We present some examples of how the mathematics of HHI works in Chart 1 beneath. The extra concentrated “Business A” scores 3400, whereas the extra aggressive “Business C” scores 900.
Chart 1: Competitiveness modifications based mostly on the variety of corporations and their market shares

Within the DOJ’s view, an HHI rating above 1800 is uncompetitive, from 1000 to 1800 is reasonably aggressive, whereas an business scoring beneath 1000 is extremely aggressive.
Though, to be truthful to the DOJ, they really use two situations when testing mergers. Since they’re involved if a merger may “considerably reduce competitors” or “are inclined to create a monopoly,” the division additionally seems to be at whether or not the merged agency’s market share is over 30% and, if that’s the case, the merger will increase the HHI by 100 factors or extra.
HHI says U.S. buying and selling is a extremely aggressive business
We will additionally apply the HHI math to U.S. fairness markets.
We present all of the totally different individuals over current years as colours within the chart beneath.
We then make some conservative assumptions:
- Including all exchanges in the identical group collectively.
- Utilizing a beneficiant worth for “Different Brokers,” that are aggregated in FINRA knowledge.
Based mostly on that, the business has an HHI rating of 874 in This autumn (chart beneath, black line). We additionally calculated the HHI for This autumn utilizing current firm-level knowledge, which isn’t out there traditionally, and acquired a rating of 900. So, by both technique, that makes the U.S. fairness market not solely extremely fragmented, but in addition extremely aggressive.
Actually, for the final two years, the HHI has been within the Extremely Aggressive vary or proper on the brink. As well as, no alternate group has a market share near 30% (bars). So, the U.S. fairness markets additionally look most like “Business C” above.
Chart 2: The fairness market is extremely aggressive and solely getting extra aggressive over time

U.S. market is simply getting much more aggressive
Since 2020, three new exchanges have been established, and there are 5 extra exchanges planning to begin operations this 12 months or early subsequent 12 months, together with 4 extra ATSs. That pushes the entire variety of venues properly over 50.
In actuality, U.S. market economics truly help new venues over current ones. So, it needs to be no shock that the HHI rating has been falling (chart above, black line). We estimate the business’s HHI rating was round 1350 at the beginning of 2019, proper in the midst of the Reasonably Aggressive zone. Now it’s properly into the Extremely Aggressive zone and heading decrease.
In brief, the U.S. market has been getting extra aggressive.
Balancing competitors with fragmentation
So, whereas regulators typically query whether or not the marketplace for buying and selling companies is aggressive, the laborious knowledge exhibits it’s not simply aggressive, however extremely aggressive.
Sooner or later, although, the query for regulators will turn out to be the best way to stability competitors with fragmentation. Fragmentation provides to fastened prices for {hardware}, dealer connections, alternate programmers and administration. For traders, alternative and search prices are greater. And never all venues care about capital formation for the latest progress firms.
That issues when you think about that the SEC’s mission consists of sustaining “environment friendly markets,” too.
Prior to now few weeks, we’ve got proven knowledge on the expansion of darkish buying and selling and the growing fragmentation of lit exchanges. Right now, there are 16 fairness exchanges, over 30 ATS venues, and greater than 100 brokers within the U.S. — they usually’re all competing to offer buying and selling companies.
That appears like loads of fragmentation available in the market, which sooner or later would possibly lead to extra prices than advantages to traders.
Right now, we’re going to make use of the identical take a look at the U.S. Division of Justice (DOJ) makes use of for mergers. That take a look at exhibits that the U.S. inventory market is, already, extremely aggressive.
The DOJ makes use of HHI as a measure of competitors
The DOJ makes use of the Herfindahl-Hirschman Index (HHI) when contemplating the antitrust implications of mergers and acquisitions. The HHI, based mostly on the work of economists Albert Hirschman and Orris Herfindahl, makes use of the market share of all of the corporations in an business to measure how concentrated it’s.
In easy phrases, the HHI index is created utilizing the weights of every firm in an business. To do that:
- Every firm’s market share is squared (this makes bigger firms depend far more).
- Then, the scores are all summed up.
We present some examples of how the mathematics of HHI works in Chart 1 beneath. The extra concentrated “Business A” scores 3400, whereas the extra aggressive “Business C” scores 900.
Chart 1: Competitiveness modifications based mostly on the variety of corporations and their market shares

Within the DOJ’s view, an HHI rating above 1800 is uncompetitive, from 1000 to 1800 is reasonably aggressive, whereas an business scoring beneath 1000 is extremely aggressive.
Though, to be truthful to the DOJ, they really use two situations when testing mergers. Since they’re involved if a merger may “considerably reduce competitors” or “are inclined to create a monopoly,” the division additionally seems to be at whether or not the merged agency’s market share is over 30% and, if that’s the case, the merger will increase the HHI by 100 factors or extra.
HHI says U.S. buying and selling is a extremely aggressive business
We will additionally apply the HHI math to U.S. fairness markets.
We present all of the totally different individuals over current years as colours within the chart beneath.
We then make some conservative assumptions:
- Including all exchanges in the identical group collectively.
- Utilizing a beneficiant worth for “Different Brokers,” that are aggregated in FINRA knowledge.
Based mostly on that, the business has an HHI rating of 874 in This autumn (chart beneath, black line). We additionally calculated the HHI for This autumn utilizing current firm-level knowledge, which isn’t out there traditionally, and acquired a rating of 900. So, by both technique, that makes the U.S. fairness market not solely extremely fragmented, but in addition extremely aggressive.
Actually, for the final two years, the HHI has been within the Extremely Aggressive vary or proper on the brink. As well as, no alternate group has a market share near 30% (bars). So, the U.S. fairness markets additionally look most like “Business C” above.
Chart 2: The fairness market is extremely aggressive and solely getting extra aggressive over time

U.S. market is simply getting much more aggressive
Since 2020, three new exchanges have been established, and there are 5 extra exchanges planning to begin operations this 12 months or early subsequent 12 months, together with 4 extra ATSs. That pushes the entire variety of venues properly over 50.
In actuality, U.S. market economics truly help new venues over current ones. So, it needs to be no shock that the HHI rating has been falling (chart above, black line). We estimate the business’s HHI rating was round 1350 at the beginning of 2019, proper in the midst of the Reasonably Aggressive zone. Now it’s properly into the Extremely Aggressive zone and heading decrease.
In brief, the U.S. market has been getting extra aggressive.
Balancing competitors with fragmentation
So, whereas regulators typically query whether or not the marketplace for buying and selling companies is aggressive, the laborious knowledge exhibits it’s not simply aggressive, however extremely aggressive.
Sooner or later, although, the query for regulators will turn out to be the best way to stability competitors with fragmentation. Fragmentation provides to fastened prices for {hardware}, dealer connections, alternate programmers and administration. For traders, alternative and search prices are greater. And never all venues care about capital formation for the latest progress firms.
That issues when you think about that the SEC’s mission consists of sustaining “environment friendly markets,” too.