The First London Rationalist Meetup

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 12 of all land.

  • Land for growith maize is 13 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.