With 50% probability, things will last twice as long as they already have.
In 1969, just after graduating from Harvard, Gott was traveling in Europe. While touring Berlin, he wondered how long the Berlin Wall would remain there. He realized that there was nothing special about his being at the Wall at that time. Thus if the time from the construction of the Wall until its removal were divided into four equal parts, there was a 50% chance that he was in one of the middle two parts. If his visit was at the beginning of this middle 50%, then the Wall would be there three times as long as it had so far; if his visit was at the end of the middle 50%, then the Wall would last 1⁄3 as long as it had so far. Since the Wall was 8 years old when he visited, Gott estimated that there was a 50% chance that it would last between 2.67 and 24 years. As it turned out, it was 20 more years until the Wall came down in 1989. This success of this prediction spurred Gott to write up his method for publication. (It appeared in the journal Nature in 1993.)
I have used this method with great success to estimate, among other things, the probability that friends will break up with their romantic partners.
I also carried out some experiments a while ago to find out what the prior probability was for me “being really sure about something”, or the probability associated to “I would be highly surprised to learn if this were false.” That is, for the feeling of being highly sure, how does that pan out?
On another direction, superforecasters have some meta-priors, such as “things will take longer than expected, and longer for larger organizations”, or “things will stay mostly as they have.”
I agree this is useful and I often use it when forecasting. It’s important to emphasize that this is a useful prior, though, since Gott appears to treat it as an all-things-considered posterior.
I have used this method with great success to estimate, among other things, the probability that friends will break up with their romantic partners.
The Lindy effect is a theory that the future life expectancy of some non-perishable things like a technology or an idea is proportional to their current age, so that every additional period of survival implies a longer remaining life expectancy. Where the Lindy effect applies, mortality ratedecreases with time.
With 50% probability, things will last twice as long as they already have.
By this you mean that if something has lasted x amount of time so far, with 50% probability the total amount of time it will have lasted is at least 2x (i.e., it will continue to last at least another x years)?
With 50% probability, things will last twice as long as they already have.
Source; see also Gott.
I have used this method with great success to estimate, among other things, the probability that friends will break up with their romantic partners.
I also carried out some experiments a while ago to find out what the prior probability was for me “being really sure about something”, or the probability associated to “I would be highly surprised to learn if this were false.” That is, for the feeling of being highly sure, how does that pan out?
On another direction, superforecasters have some meta-priors, such as “things will take longer than expected, and longer for larger organizations”, or “things will stay mostly as they have.”
I agree this is useful and I often use it when forecasting. It’s important to emphasize that this is a useful prior, though, since Gott appears to treat it as an all-things-considered posterior.
William Poundstone uses this example, too, to illustrate the “Copernican principle” in his popular book on the doomsday argument.
In my head, I map this very similarly to the German tank problem. I agree that it’s a very useful prior!
Yes, I think that this corresponds to the German tank problem after you see the first tank.
Here is a Wikipedia reference:
Yep, exactly right.