Tag: Copernican Principle

Nassim Taleb: The Winner-Take-All Effect In Longevity

Nassim Taleb elaborates on the Copernican Principle, a concept first introduced on Farnam Street in How To Predict Everything.

For the perishable, every additional day in its life translates into a shorter additional life expectancy. For the nonperishable, every additional day implies a longer life expectancy.

So the longer a technology lives, the longer it is expected to live. Let me illustrate the point. Say I have for sole information about a gentleman that he is 40 years old and I want to predict how long he will live. I can look at actuarial tables and find his age-adjusted life expectancy as used by insurance companies. The table will predict that he has an extra 44 to go. Next year, when he turns 41 (or, equivalently, if apply the reasoning today to another person currently 41), he will have a little more than 43 years to go. So every year that lapses reduces his life expectancy by about a year (actually, a little less than a year, so if his life expectancy at birth is 80, his life expectancy at 80 will not be zero, but another decade or so).

The opposite applies to nonperishable items. I am simplifying numbers here for clarity. If a book has been in print for forty years, I can expect it to be in print for another forty years. But, and that is the main difference, if it survives another decade, then it will be expected to be in print another fifty years. This, simply, as a rule, tells you why things that have been around for a long time are not “aging” like persons, but “aging” in reverse. Every year that passes without extinction doubles the additional life expectancy. This is an indicator of some robustness. The robustness of an item is proportional to its life!

This is the “winner-take-all” effect in longevity.

The main argument against this idea is the counterexample — newspapers and traditional telephone lines come to mind. These technologies, widely considered inefficient and dying, have been around for a long time. Yet the Copernican Principle would suggest they will continue to live on for a long time.

These arguments miss the point of probability. The argument is not about a specific example, but rather about the life expectancy, which is, Taleb writes “simply a probabilistically derived average.”

Perhaps an example, from Taleb, will help illustrate. If I were to ask you to guess the life expectancy of the average 40 year old man, you would probably guess around 80 (at least that's what the actuarial tables likely reveal). However, if I now add that the man is suffering from cancer, we would revisit our decision and most likely revise our estimate downward. “It would,” Taleb writes, “be a mistake to think that he has forty four more years to live, like others in his age group who are cancer-free.”

“In general, the older the technology, not only the longer it is expected to last, but the more certainty I can attach to such statement.”

***

If you liked this, you'll love these three other Farnam Street articles:

The Copernican Principle: How To Predict Everything — Based on one of the most famous and successful prediction methods in the history of science.

Ten Commandments for Aspiring Superforecasters — The ten key themes that have been “experimentally demonstrated to boost accuracy” in the real-world.

Philip Tetlock on The Art and Science of Prediction — How we can get better at the art and science of prediction, including diving into makes some people better at making predictions and how we can learn to improve our ability to guess the future.

Source

The Copernican Principle: How To Predict Everything

I ran across an old (1999) New Yorker article that introduces us to J. Richard Gott III, a Princeton astrophysicist and some of his ideas on prediction.

The core idea is that — despite what we'd like — we are not that special. So when we encounter something, we are unlikely to be doing so at a special time in its life.

“On May 27, 1993, I looked up all the plays that were listed in The New Yorker—Broadway and Off Broadway plays and musicals—and called up each of the theatres and asked when each play had opened,” Gott said. “I predicted how long each would run, based solely on how long it had been running already. Forty-four shows were playing at the time. So far, thirty-six of them have closed, all in agreement with my predictions of how long they would last. And the others, which are still running, are also within the range I'd predicted.”

It must be said that Gott's predictions are, well, broad. He predicted, for instance, that “Marisol,” which had been open for a week when he called the theatres, would close in less than thirty-nine weeks; it lasted 10 more days. To “Cats,” which had then been running for three thousand eight hundred and eighty-five days, Gott assigned a longevity of not less than a hundred days and not more than four hundred and fourteen years.

The significance of Gott's approach rests in its competence in addressing issues previously inaccessible to scientific inquiry, such as, say, trying to predict how long the human species will endure.

“As time goes on, you'll understand. What lasts, lasts; what doesn't, doesn't. Time solves most things. And what time can't solve, you have to solve yourself.”

― Haruki Murakami

“My approach is based on the Copernican principle, which has been one of the most famous and successful scientific hypotheses in the history of science,” Gott said. “It's named after Nicolaus Copernicus, who proved that the earth is not the center of the universe; and it's simply the idea that your location is not special. The more we've learned about the universe, the more non-special our location has looked. The earth is orbiting an ordinary star in an ordinary galaxy. The reason the Copernican principle works is that, of all the places for intelligent observers to be, there are, by definition, only a few special places and many non-special places. So you're simply more likely to be in one of the many non-special places.”

The predictions that I make are based on applying this principle to time. I first thought of it in 1969. I'd just graduated from Harvard and was traveling around Europe, and I visited the Berlin Wall. People at the time wondered how long the Wall might last. Was it a temporary aberration, or a permanent fixture of modern Europe? Standing at the Wall in 1969, I made the following argument, using the Copernican principle. I said, Well, there's nothing special about the timing of my visit. I'm just travelling—you know, Europe on five dollars a day—and I'm observing the Wall because it happens to be here. My visit is random in time. So if I divide the Wall's total history, from the beginning to the end, into four quarters, and I'm located randomly somewhere in there, there's a fifty-percent chance that I'm in the middle two quarters—that means, not in the first quarter and not in the fourth quarter.

Let's suppose that I'm at the beginning of that middle fifty percent. In that case, one-quarter of the Wall's ultimate history has passed, and there are three-quarters left in the future. In that case, the future's three times as long as the past. On the other hand, if I'm at the other end, then three-quarters have happened already, and there's one-quarter left in the future. In that case, the future is one-third as long as the past.

The Wall was 8 years old at the time.

“So I said to a friend, ‘There's a fifty-percent chance that the Wall's future duration will be between two-thirds of a year (I believe this should be two and two-thirds of a year – i.e. 1/3 of 8) and twenty-four years.' Twenty years later, in 1989, the Wall came down, within those two limits that I had predicted. I thought, maybe I should write this up.”

Recently, it's come to be understood that systems may behave chaotically and therefore be unpredictable. You know, a butterfly in the Amazon can affect the weather thousands of miles away, that sort of thing. This has led some people to say that predicting the future of complex systems is impossible. Which is true if you are concerned with the precise specifics. To predict the name of the President of the United States in the year 2085, for instance, is impossible. But if you ask the right question maybe you can get an interesting answer.

As for the question of how long the human species will last Gott offers some wise words.

When the author of the New Yorker article, Timothy Ferris, asked his friends how long humans would last, “most people predicted either that humans beings will last less than two hundred years or that we're good for more than ten million years.” To which Gott responded, “That's because people like to think they're living in special times. We like to think of ourselves as near the beginning of things, or in an apocalyptic situation near the end. It's more dramatic that way. A lot of people might say, ‘Oh, but we are in a special epoch. We're in the epoch when men first went to the mood, when we discovered genetic engineering, nuclear energy, and so forth.' My answer to this is that the Copernican principle predicts that you will be living in a high-population century—most people do, just as most people come from cities with higher than average populations, in larger than average nations. It's people who make discoveries, so if you live when there are more people around, you should expect to live in an age when a lot of interesting discoveries are being made.”

***

Still curious? Gott is the author of Time Travel in Einsthttps://www.farnamstreetblog.com/wp-admin/post.php?post=7149&action=edit#ein's Universe and Sizing Up the Universe: The Cosmos in Perspective.