For 538 specifically, can start by reading their own evaluations, as written in their helpfully titled "How Good Are FiveThirtyEight Forecasts?"[1]. You can the

For 538 specifically, can start by reading their own evaluations, as written in their helpfully titled "How Good Are FiveThirtyEight Forecasts?"[1]. You can then look up keywords describing their methodology to understand strengths/limitations of those methods. On a broader scale, what you are asking about is called a "Scoring Rule". Wikipedia, as usual, provides an overview[2]. You can take the mean of a forecaster's score, which allows you to compare forecaster methodologies. I'm not sure why your comment needed to be so aggressive. [1] https://projects.fivethirtyeight.com/checking-our-work/ https://projects.fivethirtyeight.com/checking-our-work/ [2] https://en.m.wikipedia.org/wiki/Scoring_rule https://en.m.wikipedia.org/wiki/Scoring_rule