Why did macroeconomists get it wrong?

The shortest answer is that macroeconomists use 32 bit precision on their computers, the aggregate economy, however, is stuck with five bits of precision in good times, about four in bad. Traders know this, that is why they look at trading bands and get excited when trading band reach a resistance level. They know that the aggregate economy is calculating a new solution with limited precision, this is Kling's recalculation.