── ── Cognitive bias
Lindy Effect
For non-perishable items — ideas, books, technologies, institutions, practices — life expectancy is proportional to current age. The longer something has survived competitive elimination, the longer its expected remaining life. Math: if survival follows a Pareto distribution with α ≈ 1, expected remaining life ≈ current age. Not nostalgia — statistical inference from a track record of passing elimination tests.
How it works
Step 1 — Items: old item (age) / new item (age) / decision / time horizon / switching cost Step 2 — Applicability: non-perishable? · elimination forces operating? · power-law plausible? · conditions changed? Step 3 — Lindy prior: old expected remaining life (≈ age) / new expected remaining life / ratio Step 4 — This-time-is-different: which conditions changed / invalidates survival evidence? / cost if wrong Step 5 — Decision: foundational → lean Lindy; exploration → lean new; document Lindy weight Step 6 — Reversibility (if going against Lindy): reversal plan / reversal signals / monitoring owner
When to use it
- user asks 'should we use this old technology or switch to something newer', 'how do I know if a book is worth reading', 'this institution has been around forever — is that meaningful', 'we should modernize / this time is different', 'how long will this practice / tool / framework last'
When not to use it
When the decision is routine and reversible, applying a formal method costs more than it returns.
Worked example
Goldman 1964, Mandelbrot 1982, Taleb 2012
The first is Albert Goldman's 1964 New Republic essay, which named the principle after Lindy's Deli on Broadway, where television comedians ate and gossiped about each other's career prospects. Goldman wrote:
Install this skill (free, MIT)
npx skills add deciqAI/knowledge-skills