The PANEL Procedure

Getting Started: PANEL Procedure

The following statements use the cost function data from Greene (1990) to estimate a variance components model. The variable PRODUCTION is the log of output in millions of kilowatt-hours, and COST is the log of cost in millions of dollars. See Greene (1990) for details.

data greene;
   input firm year production cost @@;
datalines;
1 1955   5.36598   1.14867  1 1960   6.03787   1.45185
1 1965   6.37673   1.52257  1 1970   6.93245   1.76627
2 1955   6.54535   1.35041  2 1960   6.69827   1.71109
2 1965   7.40245   2.09519  2 1970   7.82644   2.39480
3 1955   8.07153   2.94628  3 1960   8.47679   3.25967

   ... more lines ...   

You decide to fit the following model to the data:

\[ C_{it}= \mr{Intercept} + {\bbeta }P_{it}+v_{i}+e_{t}+{\epsilon }_{it} \; \; i=1, {\ldots }, \mi{N} ; \; t=1, {\ldots }, \mi{T} \]

where ${C_{it}}$ and ${P_{it}}$ represent the cost and production, and ${v_{i}}$, ${e_{t}}$ and ${{\epsilon }_{it}}$ are the cross-sectional, time series, and error variance components.

If you assume that the time and cross-sectional effects are random, you are left with four possible estimators for the variance components. You choose Fuller-Battese.

The following statements fit this model:

proc sort data=greene;
   by firm year;
run;

proc panel data=greene;
   model cost = production / rantwo vcomp = fb;
   id firm year;
run;

The PANEL procedure output is shown in Figure 27.1. A model description is printed first, which reports the estimation method used and the number of cross sections and time periods. Fit statistics and variance components estimates are printed next. A Hausman specification test compares this model to its fixed-effects analog. Finally, the table of regression parameter estimates shows the estimates, standard errors, and t tests.

Figure 27.1: The Variance Components Estimates

The PANEL Procedure
Fuller and Battese Variance Components (RanTwo)
 
Dependent Variable: cost

Model Description
Estimation Method RanTwo
Number of Cross Sections 6
Time Series Length 4

Fit Statistics
SSE 0.3481 DFE 22
MSE 0.0158 Root MSE 0.1258
R-Square 0.8136    

Variance Component Estimates
Variance Component for Cross Sections 0.046907
Variance Component for Time Series 0.00906
Variance Component for Error 0.008749

Hausman Test for Random Effects
Coefficients DF m Value Pr > m
1 1 26.46 <.0001

Parameter Estimates
Variable DF Estimate Standard
Error
t Value Pr > |t|
Intercept 1 -2.99992 0.6478 -4.63 0.0001
production 1 0.746596 0.0762 9.80 <.0001