Part of the The Bayesian Investor — A Primer for the CIO series.

The One Idea Behind Everything

Before the phases, hold onto a single image.

Imagine a bookmaker setting odds on a match. Before the first whistle, he has a price based on his initial read of the two teams — call it his starting belief. Then the match starts. A striker gets injured. A goal goes in. The crowd changes mood. With every new piece of information, the bookmaker does not throw away his price and start from zero. He adjusts it — smoothly, continuously, weighing each new fact against what he already believed. And crucially, he always knows how sure he is: early in the match his price is nervous and can swing; late in the match, with the score settled, his price is firm.

That is the entire philosophy of this roadmap, in one picture:

Start with a belief. Update it as evidence arrives. Always know how sure you are.

Every phase in this plan is just a more powerful, more automated version of the bookmaker’s craft. Phase 1 teaches the basic move (updating a belief). Phase 2 turns it into a modeling discipline. Phase 3 makes it fast enough to track things that move continuously. Phase 4 wires it into the way your firm actually invests. Let’s walk through each.