How Good Are FiveThirtyEight Forecasts?

So let’s group every MLB game prediction (not just those from September 2018) into bins — for example, we’ll throw every prediction that gave a team between a 37.5 percent and 42.5 percent chance of winning into the same “40 percent” group — and then plot the averages of each bin’s forecasted chances of winning against their actual win percentage. Brier skill scores tell us how much more valuable our forecasts are than an unskilled estimate, one that is informed by historical averages — e.g., a guess that every baseball game is roughly 50-50. Here’s how our MLB games forecast compares with all our other forecasts, based on their Brier skill scores.

Source: projects.fivethirtyeight.com