I love it when someone makes lots of predictions and then we can see their track record after the fact. Here's a collection of links to track records for anyone/anything interesting that has them tabulated, AFAIK.
The basic idea is that someone can write down specific, public predictions about the world with probabilities attached, like "60% chance that X wins the 2020 election." If they make a lot of predictions, they can then come back and assess whether their overall body of work was "well calibrated," which means that things they thought would happen 60% of the time happened 60% of the time; things they thought would happen 80% of the time happened 80% of the time; etc.
This is done using a "calibration curve" (most of the links below explain how the curve works; this explanation is pretty compact).
FiveThirtyEight HyperMind, which contracts to create predictions. A few individuals: Scott Alexander (this links to year-by-year track records, though I wish all the years were combined in one place). @peterhurford Twitter predictions (and summary). Gwern.