[seanhunter]

This is a talking point that is being put about by people (eg Jacob Rees-Mogg) who supported Brexit in an attempt to discredit the bad news. In research, the IMF's forecasting accuracy for GDP for G7 nations is pretty good and has been reasonably accurate over time. For example https://www.imf.org/en/Publications/WP/Issues/2016/12/30/How... , https://www.imf.org/en/Publications/WP/Issues/2021/08/06/An-... and https://www.heritage.org/trade/report/how-reliable-are-imf-e... but you can find other sources.