Writing in the FT he says:
I think forecasting in a complex world is a poor test of expertise because luck is the overwhelming success factor. … The wonderful thing about a forecast is that both the forecaster and his audience feel that something profound has been expressed. And nobody will remember the forecast anyway.
I’m not sure that’s wholly true: forecasters seem to spend a lot of time disavowing their predictions and claiming that the narrative is the important thing. Of course, they still publish headline figures and institutions such as the Bank of England, who only publish a range, get regularly criticised for being too vague. Even if you don’t believe Harford’s explanation, those facts need to be reconciled somehow.