Why Markets Are Non‑Ergodic and Path Dependent

Richard Brennan returns this week to explore how markets truly move - not through randomness or rationality, but through impact, feedback, and memory. What begins with a single trade builds into structure, not pattern; alignment, not noise. Drawing from neuroscience and fractal geometry, Rich challenges the idea that markets can be understood without understanding interaction. The episode builds toward a pointed exchange on position sizing - closed equity versus dynamic exposure - not as a technical footnote, but as a reflection of first principles. In a system where the path shapes the outcome, how you define risk... often reveals how you think the world works.

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Episode TimeStamps:

00:00:00 – Welcome to the Systematic Investor Series

00:00:23 – Niels’ intro, show setup, and warm welcome to Rich

00:00:57 – Heatwave down under: context and small talk

00:02:10 – Rich: divided brain, AI vs embodiment, and markets needing rules

00:07:50 – AI’s edge shrinks prediction windows; why that helps trend following

00:10:35 – Gold’s violent selloff; electricity vs oil as the new macro lens

00:14:51 – “Trend heaven”: why the backdrop now looks robust

00:18:12 – Post-GFC compression vs today’s decoupling and trends

00:22:43 – Impact and reflexivity: trades reshape the next trade

00:28:23 – Non-ergodic markets: path dependence beats Gaussian assumptions

00:35:48 – Volatility ≠ risk: compression warehouses latent tail risk

00:40:08 – Engineer robustness, don’t optimize to statistics

00:49:41 – From micro impulses to structure: feedback builds trends

00:50:06 – Patterns vs structure; outliers as phase transitions

00:55:00 – Ensemble design: behavioral (not correlational) diversification

01:03:05 – Survival first: closed-equity sizing in a non-ergodic world

01:05:43 – Niels’ counterpoints: dynamic sizing, flows, and “cutback” debate

01:12:20 – Rich: why he frames it as outlier hunting

01:16:30 – Wrap-up, programming notes, and disclaimer

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