Simon Johnson notes:
We don’t know how much of banking profits in recent years were illusory
and should not have been booked as GDP. In fact, it would not be a big
surprise if – eventually – we go back and mark down our true production
of goods and services in 2007 by 2 or even 5 percent. In this sense,
we face a statistical situation similar to that of the Soviet Union at
its demise – once they figured out that all their military production
had no real value, they had to reduce measured GDP sharply.
Don't forget to make another adjustment for the real value of health care and whether it rose proportionately with expenditure.