The Washington Post
Originally posted 9 Jan 20
Here is an excerpt:
The researchers specifically wanted to know whether the revisions were more accurate than the originals.
In theory, there are a lot of reasons to believe this might be the case. A person would presumably revise a prediction after obtaining new information, such as an analyst’s match forecast or a team roster change.
In practice, however, the opposite was true: Revised forecasts accurately predicted the final match score 7.7 percent of the time. But the unaltered forecasts were correct 9.3 percent of the time.
In other words, revised forecasts were about 17 percent less accurate than those that had never changed.
So where did the second-guessers go wrong? For starters, the researchers controlled for match-to-match and player-to-player variation — it isn’t likely the case, in other words, that matches receiving more revisions were more difficult to predict, or that bad guessers were more likely to revise their forecasts.
The researchers found that revisions were more likely to go awry when forecasters dialed up the scores — by going, say, from predicting a 2-1 final score to 3-2. Indeed, across the data set, the bettors systematically underestimated the likelihood of a 0-0 draw: an outcome anticipated 1.5 percent of the time that actually occurs in 8.4 percent of matches.
The info is here.