...Hudson River Trading LLC (HRT) has a profitable principal trading and market-making franchise that is focused on expanding its trading strategies across asset classes and regions. However, its business relies on higher-risk, less stable principal trading revenue that depends on market volume and volatility. Capitalization has improved because of strong earnings, and despite the considerable growth of the balance sheet. As of Sept. 30, 2023, HRT's risk-adjusted capital (RAC) ratio was a solid 14.3%, an improvement from 10.9% at year-end 2022, owing largely to earnings retention and lower market risk amid declining market volatility. However, the RAC ratio for the firm could be volatile--its continued expansion increases market risk, and it carries riskier, capital-intensive overnight positions. To offset this potential volatility, the firm would need a RAC that is significantly and consistently above 10%....