What percentage of the world’s airports are in the USA? (Answer below the fold.) Take a guess. Now, take another guess, different from the first one, and average them. According to research reported on in
This effect is because you tend to guess in regular interval jumps. Like fives or tens. So your first guess is closest, and the next is 10% away in the right direction. Later guesses might tap unconscious brain work. 20% and 25% for me.
Just a note: the paper does not claim that the average is always better than either guess! Only that you should expect it to be so. Of note, second guesses were worse than first guesses (overall, not always), but it was still better to average (overall, not always).
Thirty Three Things (v. 68)
1. The Market and Human Nature -- from a 2005 QA with the conservative scholar Roger Scruton (via Rod Dreher): MG: What deleterious consequences result from the "free market ideology" you mention? Are there particular economic arrangements that co...
Daniel Wolfe, Gwern: The Delphi method is different from but related to Delphi pools, which (IIRC) were initially just averages of guesses by a set of people but very soon incorporated betting on outcomes, essentially becoming prediction markets ( http://en.wikipedia.org/wik... ), a topic Robin Hanson has written a lot about. See http://hanson.gmu.edu/ and search OB for those.
I guessed 25%, but I had an unfair advantage - I designed NASA's airspace simulator, and had a list of all the international airports in the world. I believe I had just under 20,000 US airports in my simulation. That would include all airports for which ETMS data is filed, but would exclude a large number of private & small-plane airports.
And when I said I guessed 25%, I was really guessing 1/4.
Yes, I thought my first guess was too high and I guessed higher the second time because that was what came to mind first. The mental sequence went more or less like this: "25%. Hmmm. That seems a little high. 35%. So maybe 15% is a better guess."
Just like Hal Finney, I guessed 25% the first time and 15% the second time. The phenomenology of second-guessing is quite interesting. Updating your original guess in one direction feels right at one moment, and the next moment what feels right is an update in the opposite direction. I moved back and forth between 15% and 35%, and only settled for the former figure because I was impatient to see the right response.
I guessed 10% and 50% - the average is 30%!
Daniel Wolfe: That's an interesting fictional analogue. How closely related to the Delphi method ( https://secure.wikimedia.or... ) are Brunner's Delphi pools?
"Airports: This entry gives the total number of airports or airfields recognizable from the air. The runway(s) may be paved (concrete or asphalt surfaces) or unpaved (grass, earth, sand, or gravel surfaces) but may include closed or abandoned installations. Airports or airfields that are no longer recognizable (overgrown, no facilities, etc.) are not included. Note that not all airports have accommodations for refueling, maintenance, or air traffic control." - Notes and Definitions
First guess 25%, based on fraction of world economy 10-20 years ago, second guess, based on the observation that poor countries have limited highway infrastructure and need more very small airports, was 10%. I suspect that the second guess is more accurate for sufficiently small airports despite what the article says. I'd give even odds on the USSR having more airports than the US for light craft and the remainder of the world more than either alone, making the world factbook number impossible. I wonder what definitions they use.Sorry Robin and Hal but experience teaches me to be something that you probably consider overconfident.
This reminds me of a novel by John Brunner, called The Shockwave Rider. In the novel, there exist these groups called Delphi Pools, which consist of a group of normal people who all make guesses as to what the turnout of something is going to be. Surprise surprise, their averaged guesstimate is actually pretty close to the mark.
So, I know it's been used in fiction before.
@"I wonder, does this second later guess say anything about the common folk-wisdom to "sleep on" important decisions?"
It suggests to me that you can't ever "start fresh for the second guess" as Hal suggested you should.
First guess 60%Second guess 40%
I wonder, does this second later guess say anything about the common folk-wisdom to "sleep on" important decisions?
I'll have to think twice before buying another lottery ticket.