Why pollsters so often seem to get it wrong

Tim Harford: the huge win suggested for Joe Biden didn't happen, but we shouldn’t expect certainty. Once again, it seems that polls have gotten the election results in America terribly wrong. Whereas the outcome wasn't the same as in 2016, where Donald Trump defeated Hillary Clinton to a lot of experts' surprise, Biden's win this time around wasn't the 'landslide' they predicted either. The Undercover Economist explores the many reasons why for the Financial Times.