Charles R. Twardy

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Forecasting Newsletter: May 2020.

Thank you for including Replication Markets! A couple of notes:

  • Yes, the survey round is potentially a Keynesian beauty contest, though it takes some doing. You're not forecasting the market round. You're forecasting the best estimate we can make using peer prediction on the independent surveys. Harvard's peer prediction algorithm has done well in previous tests, and in theory takes a lot of coordination to defeat.* The truth is probably a good bet. We'll know more in December.
  • We had originally planned to use the output of surveys to set the market starting prices - but it made for a very messy experimental design. So we used a 70% accurate decision tree. It wasn't intended to be secret - I thought we had stated it fully but searching the site I find only oblique references.

*We got to test that a bit in Round 8 when we discovered a coordinated "attack" that accounted for ~1/3 of our surveys. Some forecasts would have changed, prizes would have been won, but neither so much as we feared.

Towards no-math, graphical instructions for prediction markets

Interesting! We designed "safe mode" to be safe against the common newbie failure of losing all cash in a few big trades. It achieved that much at least. Each trade spent max of about *1%* of your cash, and moved it at most halfway towards your goal. A dedicated newbie could still burn cash, but it took effort.

Still, from your report, that may have happened more than I thought. If so, it may not even have achieved its main design goal. :-(

"The worst thing" was indeed atrocious. We fixed that fairly quickly, but ... ugh.

Thanks for the thoughtful critique. We're about to reuse the engine. I'm giving this some thought.