The year is 1987. Jeff Yass is sitting at a poker table — not a trading desk — and that, more than anything, tells you what kind of trader he would become. Yass had spent years treating cards as a laboratory for expected value. When he co-founded Susquehanna International Group that same year, he simply moved the laboratory to the options market.

But the early years were bruising in ways that rarely make the highlight reel. Yass and his partners were mathematically sharp, but markets are not poker tables with fixed rules. Liquidity evaporates. Counterparties behave irrationally for longer than a model predicts. The team had to learn, painfully, that being right on probability and being right on timing are two very different things.

CONCEPTStatistical arbitrage seeks to profit from pricing inefficiencies using probability — not certainty.
WARNINGA statistically sound trade can still lose money if position sizing and timing are ignored.
KEY IDEAYass trained his traders in poker before markets — expected value thinking transfers directly.

What Susquehanna eventually got right was systematising the way traders think about edge. New recruits famously spent months studying game theory and poker before touching an order ticket. The firm's view: if you cannot calculate expected value at a card table under pressure, you cannot do it when a market is moving against you at speed. That discipline — cold, probabilistic, unemotional — became the firm's actual product.

Edge Over Many Trades vs Single Outcome 10 50 100 250 500 Number of Trades Cumulative P&L Statistical edge (many trades) Single trade outcome (noisy)

The lesson that transfers to everyday traders is uncomfortable: most people manage individual trades when they should be managing a process across hundreds of trades. Yass never agonised over a single losing position — he agonised over whether the underlying probability model was sound. Traders interested in this framework can explore statistical arbitrage on Investopedia, study the mechanics of expected value on Investopedia, or read the broader context of Susquehanna's approach via Susquehanna International Group on Wikipedia.

Yass remains one of the most private figures in professional trading — no memoir, no masterclass, no victory lap. The silence is, in its own way, the lesson.

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