Until about 3 days ago, I was convinced that claims that mass shootings were increasing in the US were due purely to media scare tactics and general human tendencies to see things as getting worse. This article made me strongly update against that.
The last 30 years of such claims are not due to anything that happened in 2011.
Sure, that's certainly a valid point. It doesn't make the people saying this in the 1980s or the 1990s or the 2000s correct in any way shape or form. And it is possible that the media's current claims are completely disconnected from the uptick. The relevant bit is updating that there really has been a statistically significant uptick. (Especially because my priors based on general declining crime rates would have been to if anything suspect the opposite.)
What is something you used to believe, preferably something concrete with direct or implied predictions, that you now know was dead wrong. Was your belief rational given what you knew and could know back then, or was it irrational, and why?
Edit: I feel like some of these are getting a bit glib and political. Please try to explain what false assumptions or biases were underlying your beliefs - be introspective - this is LW after all.