2. /**** LR test for heteroscedasticity ******/
xtgls y x1 x2 x3 x4 x5, i(country) t(year) igls panels(heteroskedastic)
estimates store hetero
xtgls y x1 x2 x3 x4 x5, i(country) t(year)
estimates store nohetero
local df=e(N_g)-1
lrtest hetero nohetero , df(`df')