/*
Lesson 16.2b: SUR Panel Data Analysis
Cost of Production for Airline Services III
*/
use gpe2;
output file = gpe\output16.3 reset;
load data[91,6] = gpe\airline.txt;
panel = data[2:91,1:2];   @ panel definition @
n=6;
t=15;

@ n should be reduced to 4, due to degrees of freedom @

/* stacked data series, by sections */
cs = ln(data[2:91,3]);    @ log cost (stacked) @
qs = ln(data[2:91,4]);    @ log output (stacked) @
pfs = ln(data[2:91,5]);   @ log fuel price (stacked) @
lfs = data[2:91,6];       @ load factor (stacked) @
xs = qs~pfs~lfs;

cs=reshape(cs,n,t)';
qs=reshape(qs,n,t)';
pfs=reshape(pfs,n,t)';
lfs=reshape(lfs,n,t)';

call reset;
_names = {"c","q","pf","lf"};

_eq=-eye(n)~eye(n)~eye(n)~eye(n);

call estimate(cs,qs~pfs~lfs);

end;