The Madoff Red Flags
Thorp's own account of investigating and rejecting Bernie Madoff's fund decades before its collapse — a case study in exactly what he looked for.
One of the book's most striking episodes: Thorp was asked to evaluate a Madoff-run fund as a potential investment in the early 1990s — nearly two decades before Madoff's Ponzi scheme finally collapsed in 2008 — and concluded something was seriously wrong, declining to invest and warning others. His method was exactly the quantitative skepticism the rest of the book demonstrates: he attempted to reverse-engineer Madoff's claimed options-based strategy from the reported returns, and found the reported performance simply could not be produced by the strategy Madoff claimed to run — the returns were too smooth, too consistently positive, and mathematically inconsistent with the actual risk the claimed strategy would have carried.
The book frames this as a direct, practical demonstration of the same mathematical-skepticism instinct that drove the blackjack and warrant-arbitrage work: rather than accepting an impressive track record at face value, Thorp's trained response was to ask whether the *mechanism* claimed to produce those returns could plausibly produce exactly that pattern of results — and when the math didn't add up, to treat that as a serious red flag regardless of how prestigious or trusted the manager appeared to everyone else.
The specific red flag Thorp identified — returns that are unrealistically smooth and consistently positive relative to the volatility any genuine version of the claimed strategy should produce — is presented as a checkable, quantitative warning sign available to any sufficiently rigorous investor, not a matter of insider knowledge or special access. A genuine options-based strategy, correctly described, should show some correlation with the volatility of its underlying positions; a track record that shows almost none is either an extraordinarily rare skill or, far more likely given base rates, evidence the reported numbers do not reflect real trading at all — exactly what Thorp concluded, correctly, decades before the fraud became public.
- Thorp evaluated and rejected a Madoff-run fund in the early 1990s, nearly two decades before the Ponzi scheme collapsed publicly in 2008.
- His method was to check whether the claimed strategy could mathematically produce the reported returns — it could not, since they were unrealistically smooth.
- This is presented as a checkable, quantitative red flag available to any sufficiently rigorous investor, not a matter of special access or insider knowledge.