Most people (including finance professionals) mis-size bets: too small, too big, or incorrectly adjust after streaks.
Optimal constant fraction ≈ Kelly (≈20% for this example); participants grasped it when explained.
“Crystal Ball / WSJ front page” trading game 📰
Players see a redacted historical WSJ front page (one day ahead) and trade on market moves; reveals news interpretation + sizing issues.
Findings:
~100 business-school players: ~52% directional accuracy, many busted, aggregate ~break-even. Sizing poor and inconsistent.
Six veteran macro traders: ~60% hit rate, selective bets, all made money.
Open experiment with AIs (Claude, GPT, Gemini, Grok): off-the-shelf Claude performed best among free models; overall AIs too aggressive but sometimes match/beat human players when crystal ball info exists.
Practical Rules & Takeaways
Sizing matters as much as selection — always decide how much to risk given expected returns and your risk aversion.
Treat risk as a cost/fee — subtract σ^2 (or σ^2/2 for Kelly-like objective) from expected returns to get true risk-adjusted performance.
Young investors: you can take more systematic risk because of human capital, but avoid extreme leverage because of frictions, costs, and psychology.
Non-professionals are unlikely to sustainably beat the market; professionals can.
Primary actionable advice: save consistently (target ~20% of income) — without saving, other planning is moot. 💾
How Elm Wealth / Amaranth approach it
Determine clients’ risk aversion via hypothetical expected equity premium (e.g., “If stocks return +4% over bonds, how much would you allocate?”) to set sizing.
Use diversified, low-cost index building blocks; dynamic asset allocation to adjust exposure by risk environment.
Offer transparent, low-fee (≈12 bps) managed solutions and tools (games, calculators) to educate clients about sizing and human-capital-aware planning.
Memorable Quotes / Nuggets
“It wasn't the selection of the trades, it was the sizing.”
“Getting your sizing right is not a zero-sum activity.”
“Taking risk is always a negative.”
“The right answer to the wrong question” — lots of concentration is right to become a billionaire, but that’s the wrong objective for most people. 🤔