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Comment by tsimionescu | Hacker News Reader

While this is very fun as a mathematical exercise, it's completely irrelevant as a real tool for getting a better understanding of unknown processes in the real world.

The law only applies for certain types of processes, and is completely wrong for other types (e.g. a human who has lived 50 years may live 50 more, but one who has lived 100 years will certainly not live 100 more). So the question becomes: what type of process are you looking at? And that turns out to be exactly the question you started with: is there a fundamental limit to this growth curve, or not.

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But if you met an alien who said they'd been alive for 100 years you wouldn't assume they're on the verge of dropping dead: you would assume they live longer. It's a rough rule for when you don't have other information, and if you're arguing against it you need to specify what other information you're using to make that argument.

But it only applies for when you have a single data point: it's more likely to be from the middle of the distribution then the edge.

So meeting exactly 1 100 year old alien makes it decent odds that's somewhere near the middle of their lifespan.

Because if you grabbed one random human, chances are you'd find someone roughly middle aged.

> Because if you grabbed one random human, chances are you'd find someone roughly middle aged.

That would only be true if the underlying distribution worked that way, which for the human population it doesn’t (global median age is 31, global average expected lifespan is 73), so for humans if you grabbed a random human, chances are you’d find someone less than middle-aged.

> The law only applies for certain types of processes

Did you even read the post? It’s an estimate in the context where you have zero information on which to base an accurate estimate. The author’s point is that if you’re making a different estimate you need to actually say what information is informing that.

Human lifespan is obviously not a case where we have zero information, so what is your point in bringing that up?

The lifespan argument shows how important it is to have more than zero information.

Yes, it is valuable to have more than zero information.

But often we don't have the information that we wish. Even more often, the information that we have leads us to a story, that severely misleads us. Reminding ourselves of the zero information version of the story, can be an antidote to being mislead that way.

Therefore it is valuable to know how to make the most out of zero information. And if we have information, to think about exactly why it leads to a different conclusion.

The argument is that it's not very valuable because it can be incredibly wrong and the priority is to get more information.

"And we have information to think" - then we don't have zero information right?

My point is that some processes you encounter will tend to show the Lindy effect, and some won't. If you want to claim that the Lindy effect should be the default assumption, it is up to you to show that it's more likely than not that a random process you encounter shows the Lindy effect. This is not at all an obvious fact, and is quite likely not even true.

So, if most processes are in fact like human lifespans, which do not show a Lindy effect, then it is completely wrong to assume that a random process that you encounter will have this property.

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