The Man Who Solved the Market: How Jim Simons Launched the Quant Revolution

The author chronicles the life of mathematician Jim Simons and the quantitative trading firm he built, Renaissance Technologies—a firm that uses mathematical models and algorithms rather than human intuition to make investment decisions. The firm's flagship Medallion fund has generated average annual returns of 66 percent since 1988, more than $100 billion in trading profits, and a track record surpassing every major investor in modern finance. The book traces Simons's path from theoretical mathematics and Cold War code-breaking to his decades-long quest to develop a computer-driven trading system, while exploring the personal tragedies and political upheaval that shaped his firm.

Born in 1938 near Boston, Simons showed a precocious fascination with numbers from age three. His father, Matty, a shoe-factory manager who regretted giving up an exciting career to do what was expected, taught Simons to pursue his own passions. Simons graduated from MIT in three years, earned a PhD in differential geometry at UC Berkeley, and made his first trades in soybean futures, experiencing a rush that planted a seed for his future career.

In 1964, Simons joined the Institute for Defense Analyses (IDA), a nonprofit that hired mathematicians to help the National Security Agency break Soviet codes. The IDA's flat, collaborative culture deeply influenced his later management philosophy. With colleagues including mathematician Lenny Baum, Simons co-authored a classified paper proposing a method of predicting stock prices using hidden Markov models, a technique for inferring hidden states from observable data. After being fired in 1967 for publicly opposing the Vietnam War, Simons chaired the mathematics department at Stony Brook University, building it into a top-tier program. In 1974, he and his former Berkeley mentor Shiing-Shen Chern published a paper introducing Chern-Simons invariants, geometric quantities that later proved relevant to string theory and quantum computing. The work earned Simons the Oswald Veblen Prize in Geometry.

By 1978, Simons craved a new challenge. He left academia to start Monemetrics, a currency-trading firm in a strip mall near Stony Brook. He recruited Baum, whose algorithm for riding currency trends produced early profits, and James Ax, a brilliant but volatile number theorist. The team built a crude computerized trading system, but when it malfunctioned and Baum's intuition-based trades produced a 40 percent loss in 1984, Simons was forced to unwind their partnership, leaving him determined to build a system free of human emotion.

Ax relocated to Huntington Beach, California, establishing Axcom Limited with data specialist Sandor Straus. Straus meticulously collected granular intraday pricing data that almost no other firm gathered. René Carmona, a French mathematician who consulted for Axcom, proposed letting computers search historical data for patterns and generate trades autonomously. Simons resisted because he could not understand why the program recommended specific trades, calling it a "black box" (85), but Ax defended the method. When the Medallion fund lost nearly 30 percent, Simons halted long-term trading, sparking a bitter feud with Ax.

Elwyn Berlekamp, a game theorist from UC Berkeley, bought most of Ax's stake in 1989 and took charge. His core insight transformed the fund: By shifting to frequent, short-term trades, Medallion could profit from a bare majority of its wagers, much like a casino. Working with Henry Laufer, a Stony Brook mathematician, and Straus, Berlekamp identified recurring patterns and built them into an updated model. Medallion scored a 55.9 percent gain in 1990, but Berlekamp grew frustrated with Simons's desire to override the system and sold his stake back in December 1990.

Simons brought Laufer back full-time in 1992. Laufer made a pivotal decision: Medallion would employ a single, unified trading model rather than separate models for different investments. He split the trading day into five-minute segments, uncovering previously undetectable short-term patterns, and developed a dynamic betting algorithm that adjusted the fund's holdings in real time. Medallion soared 71 percent in 1994, but Simons knew the fund was constrained by commodity markets. To grow, he needed to crack stock trading.

In 1993, Nick Patterson, a British cryptologist who had recently joined Renaissance, recruited Peter Brown and Robert Mercer from IBM's speech-recognition group, where they had used hidden Markov models and the Baum-Welch algorithm, a training method for such models, to build systems that learned from data. Brown was blunt and commercially minded; Mercer was taciturn and deeply suspicious of government. The firm's existing stock-trading system failed to execute trades properly, and Simons gave Brown and Mercer a six-month ultimatum. David Magerman, a computational linguist who joined Renaissance in 1995, discovered bugs in Mercer's code, and the system began generating gains. Brown and Mercer then built a monolithic, automated trading system of half a million lines of code that self-corrected and optimized the portfolio throughout the day.

By 1997, Medallion managed over $900 million, and Simons merged the stock fund into it. He established defining principles: fully shared source code, compensation tied to overall fund performance, and an insistence on collaboration. In September 1996, Simons's son Paul was killed in a cycling accident at age 34. The 1998 collapse of Long-Term Capital Management reinforced a key lesson: Never fully trust a model. When the dot-com bubble burst in March 2000, Medallion lost roughly $300 million in days as a momentum signal (a rule that automatically buys rising investments on the assumption the trend will continue) continued buying into the downturn. Simons overrode the system, the team ditched the faulty signal, and the fund recovered to gain 99 percent for the year.

In 2001, Renaissance began digesting vast new data categories. Brown developed basket options with Deutsche Bank and Barclays, financial instruments that amplified Medallion's leverage far beyond competitors while shifting enormous risk to the banks. The options also enabled the firm to claim profits as long-term capital gains despite holding positions for days; the IRS later ruled this treatment improper, and a 2014 Senate subcommittee accused the firm of underpaying taxes by $6.8 billion. In July 2003, Simons's son Nicholas drowned while freediving in Bali.

Simons launched the Renaissance Institutional Equities Fund (RIEF) in 2005 for longer-term signals. Investors poured $35 billion into RIEF, but its returns proved modest. In August 2007, a correlated sell-off among quantitative funds caused Medallion to lose over $1 billion in a week; Simons overrode the system, the fund recovered, and it gained 86 percent for the year. During the 2008 financial crisis, Medallion soared 82 percent, but RIEF dropped about 17 percent and investors fled. By 2010, Simons handed the co-CEO title to Brown and Mercer.

As Simons devoted more time to philanthropy, committing $100 million to autism research and launching Math for America, a nonprofit supporting math and science teachers, Mercer's political activities intensified. The Mercers invested $10 million in Breitbart News and funded Cambridge Analytica, an analytics firm; Mercer's daughter, Rebekah Mercer, became the family's political face. During the 2016 presidential campaign, the Mercers became Donald Trump's largest financial backers, and Rebekah persuaded Trump to hire Steve Bannon as a senior campaign adviser and Kellyanne Conway as a campaign strategist, moves credited with stabilizing the campaign. Magerman confronted Mercer by phone; Mercer argued that the Civil Rights Act had "infantilized" African Americans (293). After Magerman publicly criticized Mercer in the Wall Street Journal, Renaissance fired him. Growing blowback prompted Simons to ask Mercer to step down as co-CEO in October 2017.

By 2019, quantitative investors represented close to a third of all stock-market trades, and Renaissance managed $65 billion. Approaching his 81st birthday, Simons was consumed by developing treatments for autism and funding a $75 million observatory in Chile to search for evidence of gravitational waves from the Big Bang. In a March 2019 lecture at MIT, he offered advice: Work with the smartest people you can find, be persistent, and be guided by beauty.