Ergodicity Changes Everything
Most of our intuitions about probability are wrong because we confuse what happens on average across many people with what happens to one person over time. These are only the same in ergodic systems, and most of life is non-ergodic.
In Russian Roulette, the expected value across 6 players is that 5 survive. But for a single player repeating the game, the long-run outcome is death. The ensemble average and the time average diverge; that's non-ergodicity.
Why this matters: - The average return of the stock market is not your return if a single bad year wipes you out - "Rational" risk-taking based on expected value can be lethal for individuals even when it's profitable for populations - Insurance, diversification, and safety margins aren't irrational; they're responses to non-ergodicity
The core distinction: - Ergodic system: What happens to the group on average = what happens to one member over time - Non-ergodic system: These diverge. Irreversible events (ruin, death, bankruptcy) make the time average worse than the ensemble average
Practical implications: - Never risk ruin, regardless of expected value; you can't recover from zero - The Kelly Criterion tells you exactly how much to bet: enough to grow, not enough to risk ruin - Risk aversion isn't irrational; it's the correct response to living in a non-ergodic world
Takeaway: Before evaluating any risk or opportunity, ask: "Is this ergodic?" If a bad outcome is irreversible, the expected value calculation is lying to you.
See also: Efficiency Is The Enemy of Resilience | The Barbell Strategy Handles Uncertainty | Skin In The Game Aligns Incentives | Avoid Ruin Above All | Hyperbolic Discounting Makes the Future Disappear
Linked from
- Adaptation Beats Optimization in Complex Environments
- Avoid Ruin Above All
- Chesterton's Fence Before You Tear It Down
- Cognitive Load Is the Real Bottleneck in System Design
- Companies Are Not Families
- Complexity Has Three Sources
- Deep Work Requires Eliminating Shallow Work
- Digital Consumption Is the Enemy of Depth
- Efficiency Is The Enemy of Resilience
- Fractalization Subdivide to Survive
- Good Scholarship Requires Intellectual Humility
- Hyperbolic Discounting Makes the Future Disappear
- Keeping Options Open Has a Hidden Cost
- Moral Hazard Arises When Risk Is Separated From Consequence
- One Percent Improvements Compound
- Population Outcomes Diverge From Individual Outcomes
- Skin In The Game Aligns Incentives
- Teach Yourself Anything in Ten Years of Deliberate Practice
- The Barbell Strategy Handles Uncertainty
- The Kelly Criterion Sizes Your Bets
- The Ludic Fallacy Life Is Not a Casino
- The Precautionary Principle for Irreversible Risks
- Wealth Is What You Don't Spend