Dan Keegan's career is distinguished by mastery of modern trading systems: He built JPMorgan Chase & Co.'s electronic execution services business and was head of institutional equities at Automated Trading Desk, a high-tech platform that Citigroup acquired in 2007. Keegan went to Citi in that $680 million deal and has since climbed a few management rungs, but there is no "technology" in his job title — not in literal terms, anyway. Promoted in May 2016 to co-head of global equities after three years as head of equities, Americas, Keegan says the business and the technology on which it runs are not really separable. "I spend more time focusing on technology now as a global head," says the 48-year-old, whose co-leader, Murray Roos, joined Citi from Deutsche Bank in 2015. "In governance and prioritization of tech spending, all decisions by definition have to be taken at a global level," Keegan adds.
He regards the bank's global reach and steady commitment to trading as advantages that could pay off handsomely as some capital-constrained rivals pull back or place bets elsewhere. One fundamental decision that Citi has made is to no longer participate in the algorithmic-strategy arms race. Rather, Citi is relying on machine learning and big data to provide the optimal path for clients to achieve their objectives. "More real-time intelligence is being built into all of our intellectual property," Keegan says, while underscoring an enduring fundamental: "There is much to be done under the banner of automation, but what can never be automated is the relationship and how we as service providers stay close to our clients and build upon the trust created over many years."
 2. Chris Isaacson Bats Global Markets  3. Bradley Peterson Nasdaq  4. Brad Levy MarkitSERV  5. Dan Keegan Citi |
 6. Glenn Lesko Bloomberg Tradebook  7. Bryan Durkin CME Group  8. Mayur Kapani Intercontinental Exchange  9. Mike Blum KCG Holdings  10. Raj Mahajan Goldman Sachs Group |
 11. Ronald DePoalo Fidelity Institutional  12. Nick Themelis MarketAxess Holdings  13. Jenny Knott NEX Optimisation  14. Billy Hult Tradeweb Markets  15. Rob Park IEX Group |
 16. Bill Chow & Richard Leung Hong Kong Exchanges and Clearing  17. John Mackay (Mack) Gill MillenniumIT  18. Paul Hamill Citadel Securities  19. Eric Noll Convergex  20. Veronica Augustsson Cinnober Financial Technology |
 21. Tyler Moeller & Joshua Walsky Broadway Technology  22. Alasdair Haynes Aquis Exchange  23. Gaurav Suri Arcesium  24. Manoj Narang Mana Partners  25. Michael Chin & Neill Penney Thomson Reuters |
 26. Robert Sloan S3 Partners  27. Anton Katz & Stephen Mock AQR Capital Management  28. Donal Byrne Corvil  29. Stu Taylor Algomi  30. Alfred Eskandar Portware |
 31. Steven Randich Financial Industry Regulatory Authority  32. R. Cromwell Coulson OTC Markets Group  33. Peter Maragos Dash Financial  34. John Fawcett Quantopian  35. Donald Ross III PDQ Enterprises |
 36. Jennifer Nayar Vela Trading Technologies  37. Dan Raju Tradier  38. Susan Estes OpenDoor Trading  39. David Mercer LMAX Exchange  40. Oki Matsumoto Monex Group |
