Profiles in Power: Who Is Ken Griffin? The Man Whose Firm Processes Your Trades, Bailed Out Its Rival, and Then Moved States to Dodge a Tax Increase

In January 2021, millions of retail investors, many of them millennials who had started investing for the first time during the pandemic, piled into GameStop.

The play was simple: a massive hedge fund had bet heavily against the stock, retail investors spotted it, and they coordinated to squeeze the short.

For about a week, it looked like the little guy was winning.

Then Robinhood halted buying.

Robinhood's biggest source of revenue was a firm called Citadel Securities which paid Robinhood for the right to execute its customers' trades.

Citadel's hedge fund had just put $2 billion into Melvin Capital, the fund that was losing billions on its GameStop short position.

And the CEO of Citadel, which owned both the market-making operation and the hedge fund, was a man named Ken Griffin.

Griffin was called before Congress. He denied any conflict of interest. The news cycle moved on. Ken Griffin is now worth approximately $50 billion. You've probably never heard him give an interview.

What Citadel actually does

Citadel operates two distinct businesses. Citadel LLC is the hedge fund, one of the most successful in history, returning around 19% annually over three decades. Citadel Securities is the market maker, the firm that executes a massive share of all US retail stock trades by paying brokerages like Robinhood, TD Ameritrade, Charles Schwab, and E-Trade for the right to route their customers' orders.

The model is called payment for order flow. When you hit 'buy' on a stock in your brokerage app, there's a very high probability Citadel Securities is on the other side of that trade. It processes roughly 40% of all US retail equity trades. It's not a middleman in the casual sense, it is the market for most retail investors.

This is the structure that generated intense scrutiny in January 2021. On one hand, Citadel Securities was the firm executing trades for the Robinhood users piling into GameStop. On the other hand, Citadel LLC had just invested $2 billion to bail out Melvin Capital, which was hemorrhaging money on its GameStop short. Two days later, Robinhood halted purchases of GameStop. The stock price collapsed. Melvin survived.

Internal Robinhood Slack messages later surfaced showing a Robinhood executive noting that Citadel wanted to speak with them about limiting payment for order flow on GameStop. Griffin testified before Congress that Citadel had no role in Robinhood's decision to halt trading. Whether you believe him depends on how much weight you put on the timing.

Who he is

Griffin was born in Florida in 1968, began trading convertible bonds out of his Harvard dorm room in 1987 with a satellite dish so he could get real-time price data, and founded Citadel in 1990 at age 22. Unlike many of the names in this series, Griffin built his money from scratch, genuinely. His edge was not connections or inheritance but an obsessive focus on quantitative modeling and risk management at a time when most of Wall Street was still running on relationship networks and gut instinct.

The model worked. Citadel was one of the only major hedge funds to survive the 2008 financial crisis without permanent damage, after nearly collapsing during it. He has since become the dominant force in market making, and one of the most prolific political donors in American history.

The tax story nobody talks about enough

In 2020, Illinois put a graduated income tax increase on the ballot. Under the proposal, people earning more than $750,000 a year would be taxed at 7.99%. For Griffin, based on his reported income, this could have cost him up to $80 million in a single year.

Griffin spent $54 million fighting the ballot measure. It failed. He had effectively bought himself an $80 million annual tax savings for $54 million. A few years later, when Illinois continued pursuing progressive tax policy, he moved Citadel's global headquarters to Miami. Florida has no state income tax.

He told reporters the move wasn't about taxes. He cited crime in Chicago. This is the man who, according to OpenSecrets, donated $107 million to outside spending groups in 2024 alone, making him one of the five largest political donors in the country. He gave $5 million to Ron DeSantis's reelection. He backed Nikki Haley for president. He has donated to both parties when it served his interests, and to neither when it didn't.

He once said, publicly, that the ultra-wealthy had insufficient influence in American politics.

Why millennials should know who he is

The market is the primary retirement vehicle for a generation that has no defined pension, no guaranteed Social Security, and limited ability to build wealth through homeownership. If you use a retail brokerage app, and at this point most people who invest do, there is a meaningful chance Ken Griffin's firm is on the other side of your trades.

Payment for order flow is legal. It is disclosed in the fine print. It is not inherently sinister. But the structure it creates, where a firm simultaneously makes markets for retail investors and runs hedge fund positions in those same markets, is a conflict of interest that has never been cleanly resolved. The SEC has proposed restricting it multiple times. The restrictions have not been implemented.

What happened in January 2021 was a moment when the architecture of the retail investing market became briefly visible. Ordinary people got a look at who is actually in the room when they hit buy. Then the story got complicated, the headlines moved on, Griffin testified, and the architecture went back to being invisible.

He is now worth $50 billion, runs the most politically active private investment firm in America, and processes your retirement trades from a tax-free state he moved to after spending $54 million to make sure his old state couldn't tax him at the same rate as everyone else.

The market is totally fair. Stay Frustrated.