Krugman discusses why people people believe things that just aren’t true: Remember “American carnage?” Donald Trump’s 2017 inaugural address was peculiar in many ways, but one of the most striking oddities was his obsession with a problem — urban crime — that had greatly diminished over the past generation. For reasons we still don’t fully understand, violent crime in America fell rapidly from around 1990 to the mid-2010s: True, there was a crime surge after the pandemic, which now seems to be ebbing. But that lay in the future. Trump talked as if crime was running rampant as he spoke. Yet if Trump had false beliefs about trends in crime, he had plenty of company. Gallup polls Americans about crime every year, and all through the great decline in violent crime a majority of Americans said that crime was increasing: Were the crime statistics misleading? Homicide numbers are pretty solid. And people behaved as if crime were falling; notably, there was a wave of gentrification as affluent Americans moved into newly safe central cities. But all the same, people told pollsters that they believed crime was rising. Why am I talking about public perceptions of crime? Well, last week, I wrote about the gap between public perceptions of a terrible economy and the reality of an economy that is doing very well by normal standards. I also noted that Americans seem relatively upbeat about their own financial circumstances; they just think that bad things are happening to other people. Not surprisingly, I got a lot of pushback.…