Dating ten years apart
Real GDP reached its low point in the second quarter of 2009, while the value of real GDI was essentially identical in the second and third quarters of 2009.
The average of real GDP and real GDI reached its low point in the second quarter of 2009.
Identifying the date of the trough involved weighing the behavior of various indicators of economic activity.
The estimates of real GDP and GDI issued by the Bureau of Economic Analysis of the U. Department of Commerce are only available quarterly.
In both the 2001- cycles, household employment also reached its trough later than the NBER trough date.