Both have to be "handled with care".

Revisions

We're all tempted to make predictions on the basis of the last data point. And even more difficult to resist is the temptation to make definitive statements on the basis of data that are sure to be revised. For instance, we see this question from Casey Mulligan, "Where's the GDP Disaster?".

Last October, when we were told that spending and incomes were about to collapse, I predicted that "real GDP will not drop below $11 trillion (chained 2000 $)."

Professor Mulligan provides this graph.

Figure from Mulligan, "Where's the GDP Disaster?"

I think this is an excellent time to recapitulate the hazards of making definitive assessments on the basis of data that are sure to be revised [0] [1]. To illustrate this point, I go back to the last recession, which according to the NBER extended from

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