I explain what I've learned from creating and judging thousands of predictions on personal and real-world matters: the challenges of maintenance, the limitations of prediction markets, the interesting applications to my other essays, skepticism about pundits and unreflective persons' opinions, my own biases like optimism & planning fallacy, 3 very useful heuristics/approaches, and the costs of these activities in general.
Plus an extremely geeky parody of Fate/Stay Night.
This essay exists as a large section of my page on predictions markets on gwern.net
: http://www.gwern.net/Prediction%20markets#1001-predictionbook-nights
You don't have very many predictions judged, so I'm not sure how reliable your worry is - only 8-11 predictions for each decile seems quite possible to just get lucky. Assuming that's not the case, you could try mechanically bumping up every prediction by 10% and see what happens.
Also I notice there are many sets of predictions of the the form X will happen in 1 month/2 months/1 year/... with a separate prediction for each time period. How are these scored? Since these types of predictions are highly correlated scoring them individually can cause people to appear over or under confident.