Susquehanna (SIG) and Hudson River Trading (HRT) have emerged as 2025’s best net improvers both in terms of volume as well as execution quality as measured by E/Q ratio (The ratio of effective spread over quoted spreads). Their January to July volume executed improved 38 and 72 percent respectively to 10.4 billion and 9.9 billion, while they bettered their median E/Q by 39 and 33 percent respectively to 0.299 and 0.341.
Median E/Q Spread Ratio Over Time
In Global Trading’s expanded Rule 605 dataset, retail execution quality trends revealed a secular shift, with Susquehanna and Hudson River Trading edging ahead of rivals on key measures even as Citadel retained its dominance in overall size and Virtu kept the second position in terms of overall executed volume. According to BMLL data analysed by Global Trading, lit continuous trading rebounded in July to 138.4 billion shares, up13.8% month on month, as volatility carried on contracting and the market buoyant.
For comparison, the five largest market makers as ranked by Rule 605 disclosures, executed the equivalent of just over 42 percent of this market activity measure with 58 billion shares traded. Citadel Securities once again ranked as the largest destination, handling 27.7 billion retail shares and producing about US$153 million in net price improvement, followed by Virtu with US$101.8 million improvement for 17.6 billion shares traded, and SIG at US$77.3 for 10.4 billion shares executed. The trio was closely followed by rapidly catching up HRT which provided retail traders with US$62.8 million improvement on 10.4 billion shares traded.
Jane Street and Two Sigma price improvement within the 605-disclosure scope totalled US$40.1 million and US$12.2 million respectively, while they executed 8.2 and 2.4 billion shares respectively. The former, Jane Street, is the only market maker to have seen its E/Q ratio degrade (higher is worse) this year going from 0.515 in January to 0.535 in July.
Previous academic studies have shown that changes in execution quality ranking can be interpreted as a clear push to gain market shares in the retail execution space by market makers. This may have occurred in 2025 with SIG and HRT; HRT declined to comment and SIG did not reply to a request for comments.
Sources have confirmed to us that HRT surpassed Citadel Securities in overall Q2 2025 trading revenues at US$2.6 billion over the latter US$2.4 billion revenue. They both were still far behind Jane Street at US$10.1 billion trading revenue for Q2 2025.
Further support for this explanation lies in the analysis of the competitive dynamics in market making across common tickers. In July, on the securities where multiple market makers were active, Susquehanna’s median E/Q outperformed Citadel by 11 basis points, while HRT bettered Jane Street by roughly 19 basis points: The gains are not solely the product of trading in “easier” or different names but reflect a genuine better execution quality.
Having run regressions against the unique features of the Rule 605 disclosure datasets we understand that order type mix and time to execution mix are also big drivers of the overall execution quality offered by market makers. The interactive chart below shows that order type is strongly correlated with E/Q spread level.
The very differentiated composition of shares executed, orders internalised by types suggests further specialisation by market makers and the corresponding routing choices made by retail brokers. These dynamics might become clearer with the adoption of the enhanced Rule 605 disclosures.
Read more: SEC amends disclosure of order execution information rule
