How can we predict how long an idea, technology, or tradition will remain relevant? One heuristic is the Lindy Effect (also known as Lindy’s Law):

The longer a thing is around, the longer it will stay around.

Here are two models: a cat and a book.

Assume when a cat is born, it has a life expectancy of 20 years. As it ages, its life expectancy may increase a little bit, but not much. A cat will not live twice as long as its expected lifespan.

Contrast a cat with a book. If a book has been in print for one year, it will likely be in print for another year. But if a book has been in print for two years, its will probably stay in print for four years. As a book ages, its expected lifespan increases!

Lindy’s Deli in New York, where the Lindy Effect was conceived.

The Lindy Effect usually applies to less-tangible things concepts ranging from ideas, companies, works of literature, traditions, and many others. The principle works because time is one of the best testers of fragility. If a concept is old, it must have endured many stressors.

The Lindy Effect reminds us not to succumb to neomania–new is not always better. Asbestos and trans fats were once heralded as successes of the 20th century, but now we’ve discovered they both cause cancer.

Never use the Lindy Effect when a situation requires high precision. A rule of thumb is not an ultra-precise measuring tool. There are technologies, such as the Internet, that will probably last much longer than twice their current lifetime. If you knew nothing else except the age of a technology, you could use the Lindy Effect to get a rough estimate for its total lifetime.

What types of things do you think the Lindy affect applies to?