Way back in April 2018, I announced a Prediction Contest, in which the person who made the best predictions on a bunch of questions on PredictionBook ahead of a 1st July deadline would win a prize after they all resolved in January 2019, which is now.
It was a bit of an experiment; I had no idea how many people were up for practicing predictions to try to improve their calibration, and decided to throw a little money and time at giving it a try. And in the spirit of reporting negative experimental results: The answer was 3, all of which I greatly appreciate for their participation. I don't regret running the experiment, but I'm going to pass on running a Prediction Contest 2019. I don't think this necessarily rules out trying to practically test and compete in rationality-related areas in other ways later, though.
Our entrants were bendini, bw, and Ialaithion, and their ranked log scores were:
This was sufficiently close that changing a single question's resolution could tip the results, so they were all pretty good. That said, bw came out ahead, and even managed to beat averaging everyone's predictions- if you simply took the average prediction (including non-entrants) as of entry deadline and made that your prediction, you'd have got -9.576568147.
The full calculations for each of the log scores, as well as my own log score and the results of feeding the predictions as of prediction time to a simple model rather than simply averaging them, are in a spreadsheet here.
I'll be in touch with bw to sort out their prize this evening, and thanks to everyone who participated and who helped with finding questions to use for it.