CONCEPT
Path Dependence
The principle that where you are constrains where you can go—the sequence of decisions already made narrows future options, producing outcomes rational actors would not choose if they could see the full trajectory.
Path dependence means history matters in ways that standard economic theory denies. Decisions compound over time such that rational choices at each step produce long-run outcomes the choosers would reject if presented the full path in advance. The developer investing fifteen years in a technology stack makes individually rational annual decisions that collectively produce total commitment to a paradigm about to break. Arthur demonstrated this operates not through irrationality but through the accumulation of sunk costs, acquired skills, institutional commitments, and psychological investments that make switching progressively more expensive. Path dependence transforms temporary advantages into permanent ones through positive feedback.
In The You On AI Field Guide
Arthur formalized path dependence mathematically in the 1980s, showing that competing technologies subject to increasing returns lock in based on early events that may be essentially random. The sequence matters more than the fundamentals. QWERTY became standard not from typing-speed optimization but because early typewriter manufacturers adopted it, touch typists learned it, the installed