The First London Rationalist Meetup

by taw2 min read4th Apr 200914 comments


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Here's a brief summarly of the first meetup. It took place on cafe on top of Waterstone bookstore on Saturday 2009-04-04, starting at 14:00 and lasting until about 17:15. Six people showed up: Tomasz (me), Michael, Will, Julian, Shane, and Marc.

We started with a game of estimation warewolf - there was 1 decider, and 3 participants, one of the dishonest. 2 people showed up later, so they joined the game as openly honest. I don't think the decider position was really necessary, we could simply randomly assign people to honest and dishonest set. Or if the dishonest guy was necessary, we were confused enough without any active help. The subject was "maize production of Mexico". We did our estimate twice. First based on what Mexicans are likely to eat. Our estimates were:

  • 100 million Mexicans
  • 3000 kcal / day / Mexican
  • 30% of their calories from maize
  • extra 50% on top of the result for animal feed, biofuels and other uses
  • giving 44.3 mln tons of maize per year

Most of the time we discussed it first, and then took the median of our guesses as the estimate. The discussion was really the fun bit, I'll give a few examples later. There was a lot of joking about anchoring effect, but I don't think there was that much of it.

Then we hid the first estimate, and tried the same question again, in a different way, estimating:

  • Land area of Mexico was 3,125,000 square km. This estimate took surprisingly long time, with paths like "USA has 4 time zones, there are 15 degrees per time zone, north Mexican border is about half of south USA border, Mexico is shaped more or less like a triangle" etc., drawing pictures from memory and taking medians of them, guessing how many times different countries are bigger than each other, and guessing from territorial changes after Mexican-American wars. I guess everybody enjoyed it so much, because we all had so many bits of information vaguely related to what we were trying to guess, but no direct estimate.
  • Land used for growing plants is 1/2 of all land.
  • Land for growith maize is 1/3 of that.
  • 10 plants per square meter.
  • 500g per plant.
  • giving 2600 mln tons of maize per year

That was almost two orders of magnitude off. I was so sure that the second estimate failed any sanity check that I took a 10000:1 bet against it (conditional on our arithmetics being correct), taking 1p against 100 pound donation to the Singularity Institute. At this point we gave our point estimates, and checked it against reality. If my notes are correct, they were:

  • Tomasz - 100 mln tons
  • Shane - 150 mln tons
  • Michael - 250 mln tons
  • Will - 75 mln tons
  • Julian - 100 mln tons
  • Marc - 650 mln tons
  • Reality (as spoken through Wikipedia) - 22.5 mln tons

So the Singularity Institute isn't getting their money, our first estimate was very accurate considering our lack of clue about the subject matter, the second was widely off, and everybody except Marc gave more credence to the first. They might have been convinced by me taking that absurd bet via Aumann's Theorem.

Errors on individual estimates were:

  • population - 109 mln Mexicans (estimate 9% low)
  • area - 1972550 km (estimate 58% high)
  • maize consumption - 400 kg / year (estimate 22% low)
  • 13% of Mexican land is arable (estimate 280% high)
  • area used for maize in Mexico - 75500 square km (estimate 588% high)
  • yield per square km - 286 ton/square km (estimate 1650% high) - this number had more doubts than any other, and it seems we were correct in our doubt

After that, we just had chat about the Cabal on Wikipedia (which doesn't exist), tvtropes, early Internet sentimentalism, option pricing, financial crisis, quantum computers, prospects of AGI, and other random subjects. We also invented a new way of paying the bill "by the bailout" - everybody puts as much money on the plate, or takes as much from it as they want, as long as the final result sum was right.

We're most likely going to do the next meeting in about a month, in the same place. Here's the picture. Please correct me if I misremembered anything important.

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