From The Big Picture:
The obvious answer is that extrapolation of current trends into infinity fails in any data set that is cyclical.
The Short Side of Long takes a swipe at the question, writing:
"The fact is, most economists are totally useless at predicting recessions.
"According to Variant Perception (I recommend reading their leading indicator economic research), 'in the past four U.S. recessions, consensus forecasts did not recognise the recession even when recessions had already started.'
"The problem with economists and other academics is that they simply extrapolate data trends, as seen in the chart above. Variant Perception goes onto argue that..."
More on recessions: