Lindy Effect  UP232

The Lindy effect is a theorized phenomenon by which the future life expectancy of some non-perishable things, like a technology or an idea, is proportional to their current age. Thus, the Lindy effect proposes the longer a period something has survived to exist or be used in the present, it is also likely to have a longer remaining life expectancy. Longevity implies a resistance to change, obsolescence, or competition and greater odds of continued existence into the future. Where the Lindy effect applies, mortality rate decreases with time. The concept is named after Lindy's delicatessen in New York City, where the concept was informally theorized by comedians.

The Lindy effect applies to "non-perishable" items, those that do not have an "unavoidable expiration date". For example, human beings are perishable: most humans live for about 80 years. So the Lindy effect does not apply to individual human lifespan: it is unlikely for a 5-year-old human to die within the next 5 years, but it is very likely for a 70-year-old human to die within the next 70 years, while the Lindy effect would predict these to have equal probability.

The origin of the term can be traced to Albert Goldman and a 1964 article he had written in The New Republic titled "Lindy's Law". The term Lindy refers to Lindy's delicatessen in New York, where comedians "foregather every night at Lindy's, where ... they conduct post-mortems on recent show business 'action'". In this article, Goldman describes a folkloric belief among New York City media observers that the amount of material comedians have is constant, and therefore, the frequency of output predicts how long their series will last:

“...the life expectancy of a television comedian is [inversely] proportional to the total amount of his exposure on the medium. If, pathetically deluded by hubris, he undertakes a regular weekly or even monthly program, his chances of survival beyond the first season are slight; but if he adopts the conservation of resources policy favored by these senescent philosophers of "the Business", and confines himself to "specials" and "guest shots", he may last to the age of Ed Wynn [d. age 79 in 1966 while still acting in movies.”

Nassim Taleb presented a version of Mandelbrot's idea in The Black Swan: The Impact of the Highly Improbable by extending it to a certain class of non-perishables where life expectancy can be expressed as power laws.

“With human projects and ventures we have another story. These are often scalable, as I said in Chapter 3. With scalable variables ... you will witness the exact opposite effect. Let's say a project is expected to terminate in 79 days, the same expectation in days as the newborn female has in years. On the 79th day, if the project is not finished, it will be expected to take another 25 days to complete. But on the 90th day, if the project is still not completed, it should have about 58 days to go. On the 100th, it should have 89 days to go. On the 119th, it should have an extra 149 days. On day 600, if the project is not done, you will be expected to need an extra 1,590 days. As you see, the longer you wait, the longer you will be expected to wait.”