Measuring Market Share
Citadel Securities has been publicly reported to handle approximately 25–40% of all U.S. retail equity trading volume at various points in recent years, based on company statements and public reporting. It is the largest designated market maker on the NYSE. Precise figures vary by source and time period. The firm's dominance in retail market-making is widely acknowledged in industry and regulatory circles.
How Concentration Developed
Citadel Securities built its market share through technology investment, competitive PFOF payments, and operational scale. As major discount brokers shifted to zero-commission models, PFOF became the primary broker revenue stream — and firms that paid the most PFOF attracted the most order flow. Citadel Securities' ability to compete aggressively on PFOF payments, backed by Kenneth Griffin's capital, allowed it to win market share from competitors.
Concentration and Competition Concerns
Market concentration in wholesale market-making raises competition concerns. If a single firm handles a dominant share of retail order flow, it may gain pricing power relative to both brokers (in setting PFOF rates) and retail investors (in execution quality). The SEC and academic researchers have examined whether concentrated market making leads to worse outcomes for retail investors. The evidence is debated, but the structural concern is legitimate.
Regulatory Attention
High concentration in any critical financial market infrastructure segment typically attracts regulatory attention. The SEC's 2022 market structure reform proposals — including order competition requirements — were in part responses to concerns about concentrated market-making. Whether regulatory action will meaningfully alter Citadel Securities' market share remains to be seen.