Lindy Effect

The longer something has survived, the longer it's likely to survive. That's the Lindy effect. A book that's been in print for 40 years has a longer expected future than a book that's been in print for 2 years. A technology that's been in use for a century has a longer expected future than one that's been in use for a decade. The logic is that non-perishable things (ideas, institutions, technologies) don't have a fixed lifespan — they're not like fruit. Every day they survive is a day they've passed a test. The longer the streak, the more robust they've proven. So conditional on having survived to date, expected remaining life increases with age. Lindy is named after Lindy's deli in New York, where comedians supposedly observed that a comic who had been performing for 20 years had about 20 years left; one who had been performing for 5 had about 5 left. The rule of thumb: expected future life is proportional to past life.

The effect is a heuristic, not a law. Some things die after a long run — empires, companies, technologies. But for the class of things that don't have a predetermined expiry (unlike humans or contracts), longevity is informative. Use it to prioritise what to read (old books have been stress-tested), what to build on (old technologies and institutions have durability), and what to bet on (the thing that's been around has passed more tests). The mistake is recency bias: assuming the new thing is better because it's new. Lindy says the old thing has a claim on the future precisely because it's old. The second mistake is applying Lindy to perishables. It's for ideas, institutions, and technologies — not for people or for assets with fixed maturity.