An econometrician has used the U. S. domestic consumption in 1921-1941 and 1945-1950 (omitted during the war of 1942-1944)

 And the time series data of wage income W, non-wage-non-agricultural income P and agricultural income A, which are estimated by the ordinary least square method  The regression equation is as follows:

The numbers in brackets below the equation are standard errors of the corresponding parameter estimators. 

This model is evaluated and some problems are pointed out.