The U.S. equity markets are the most robust in the world and continue to be among the deepest, most competitive, most liquid and most efficient. They are also among the most regulated.

The U.S. equity markets facilitate capital formation. They are the most robust in the world and continue to be among the deepest, most competitive, most liquid and most efficient. They are also among the most regulated. 

Efficient and resilient market structure is key to sustaining investor confidence and participation in the equity markets. Market structure can drive liquidity and trade costs for businesses and investors alike. Therefore, market participants continually strive to create the most efficient markets. This includes adapting new technologies to achieve operational efficiencies, searching for new ways to transact and, generally, optimizing market structure to maximize efficiencies. Market makers exist to provide liquidity in securities and execute customer trades, playing an important role in equity market structure by enabling liquidity and balancing buy and sell demand. Importantly, investors, particularly retail investors, benefit from this efficiency and resiliency through reduced costs including no or low commissions, best execution and competition. All market participants seek to drive innovation to further improve equity market efficiency, resiliency and most importantly the benefit to investors. However, regulators must carefully weigh the impact of any changes on investors. Specifically, as the SEC considers proposing major changes to our current equity market structure system, it is critical that any changes be data-driven with robust cost-benefit analysis. 

There were several significant updates in 2024: 

• In March 2024, the SEC adopted a final rule amending Rule 605, modernizing disclosure requirements for order execution.  

• In September 2024, the SEC adopted amendments to Regulation NMS. The amendments establish a new minimum $0.005 quoting increment for certain tick constrained stocks; reduces the maximum access fee cap for exchange transactions; requires exchanges to disclose transaction fees at the time of execution; and accelerates the implementation of the new round lot requirements and the display of odd-lot information to enhance the transparency of better priced orders. 

• In October 2024, two national securities exchanges filed a challenge to the amendments to Rules 610 (access fees) and 612 (tick sizes) in the D.C. Circuit. In December 2024, the Commission stayed the effectiveness of the tick size and access fee amendments pending the outcome of the exchanges’ litigation. The remaining amendments to Regulation NMS are not affected by the stay.      

Important Links

SIFMA has long called for a review of equity market structure, having previously presented recommendations designed to enhance the current structure to the SEC and Congress in 2013, 2014 and 2017. We continue to be engaged on these issues and call attention to the following important resources:

SIFMA Comments

• SIFMA Comments on the SEC’s Equity Market Structure Proposals
• The SIFMA Podcast: Creating Risk by Fixing What’s Not Broken
• Penn + Wall Blog Post: 1,600+ Pages of “Solutions” in Search of a Problem

SIFMA Insights

• The ABCs of Equity Market Structure
• Market Metrics & Trends

SIFMA Research

• US Equity & Related Statistics
• Research Quarterly: Equities

Conferences & Webinars

• Market Structure Conference (November 19-20, 2025) 
• Equity Market Structure Roundtable (April 19, 2023)
• The SIFMA Podcast: Top Five Takeaways from SIFMA’s 2023 Market Structure Conference