st: Adding fixed time and country effects in frontier (SFA)‏‏

[Ravi Singh <des_c_@hotmail.com>]

Dear all, 
Im analyzing panel data of railway companies in 15 EU- countries between 1990-2008 to observe the inefficiency of the companies. There is one output, namely passengerskm and three inputs, namely length lines, rolling stock and staff. I also added the variables networkdensity (land area m2/length lines), and vertical separation (0 or 1) and horizontal separation (0 or 1) to analyze the effect of reforms in different countries in different year on the output. 
My data:
Country            Year    PassengersKM   LengthLines  RollingStock  VerticalSep  HorizontalSep 
Austria             1990   ....                          .....                    .....                    0                      0
Austria             1991   ....                          .....                    .....                    1                      0
Austria             1992   ....                          .....                    .....                    1                      0
....
Belgium           1990   .....                         .....                    .....                   0                       1

Now I applied the command 'frontier PassengersKM LengthLines RollingStock Staff Networkdensity VerticalSep HorizontalSep' to perform the stochastic frontier analysis to observe the inefficiency. Results: there is no inefficiency in this model. This is the first time Im using Stata. Can somebody give me an advice how I could implement time and country effects in Stata for this model?

Regards, 

Ravi 		 	   		  

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