What Eric seems to be saying has an analogue in weather forecasting. In the language of this discipline, verifying forecasts of low probability events is difficult because your sample size is to small to get an accurate picture of skill. And not only do you need to be able to pick the events accurately, your forecast model should predict events with roughly the probability that they actually occur – forecast a hurricane with 100% probability every day and you are a ‘stopped watch’.
Not that this can really apply in economic forecasting, where not only do we not predict the future by applying well known dynamical rules to the current state, but it’s far from clear that we know what those dynamical rules are. Instead we have a range of experts each emphasising their own special interest bit of sub-dynamics.
Eric mentions Marx, and no doubt there are those who are again suggesting that the current crisis is a vindication of Marx. These are the people who read ‘The Communist Manfiesto’ pamphlet, and put down Capital before finishing the first chapter (Mick Hume at Spiked has a nice article about this). Or who skipped straight to Trotsky. Marx is interesting for his attempt to describe the dynamical principles behind the capitalist economies of his day. Whether he’s useful today is another question.