# PS10.6, for Example 10.5 for the Dickey-Fuller test
open data9-2 
genr time
# generate log of money supply
genr Y = ln(M)
# generate delta Y
genr DY = diff(Y)
# lag DY once
genr Y1 = Y(-1)
# delta Y(-1)
genr DY1 = DY(-1)
# reset starting obs to omit two observations
smpl 1962 ;
# estimate unrestricted model U
ols DY const time Y1 DY1
omit time Y1