[Gretl-users] R-squared for Prais-winsten in Gretl higher than in stata 8

Hi everybody, I'm new to Gretl and was just trying out a couple of things. I have one question: when I run a normal OLS on a dataset I have, I get an R-squared of 0.54 (see below) Model 4: OLS estimates using the 28 observations 1981-2008 Dependent variable: Market              coefficient   std. error   t-ratio   p-value   --------------------------------------------------------   const      -0.0537645    0.0158677    -3.388    0.0023   ***   GDP         2.61979      0.465478      5.628    6.46e-06 *** Mean dependent var   0.023904   S.D. dependent var   0.060574 Sum squared resid    0.044660   S.E. of regression   0.041445 R-squared            0.549209   Adjusted R-squared   0.531871 F(1, 26)             31.67644   P-value(F)           6.46e-06 Log-likelihood       50.44212   Akaike criterion    -96.88424 Schwarz criterion   -94.21983   Hannan-Quinn        -96.06970 rho                  0.264994   Durbin-Watson        1.356766 This is a time-series, and I wanted to see what a Prais-Winsten regression output would be like: Performing iterative calculation of rho...                  ITER       RHO        ESS                    1      0.26499   0.0401631                    2      0.40328   0.0387053                    3      0.46859   0.0382796                    4      0.49500   0.0381643                    5      0.50490   0.0381302                    6      0.50850   0.038119                    7      0.50980   0.0381152                    8      0.51027   0.0381152 Model 5: Prais-Winsten estimates using the 28 observations 1981-2008 Dependent variable: Market              coefficient   std. error   t-ratio   p-value   -------------------------------------------------------   const      -0.0347002    0.0188278    -1.843    0.0768  *   GDP         1.81362      0.426344      4.254    0.0002  *** Statistics based on the rho-differenced data: Mean dependent var   0.023904   S.D. dependent var   0.060574 Sum squared resid    0.038114   S.E. of regression   0.038287 R-squared            0.615716   Adjusted R-squared   0.600936 F(1, 26)             17.61559   P-value(F)           0.000279 Log-likelihood       52.66109   Akaike criterion    -101.3222 Schwarz criterion   -98.65776   Hannan-Quinn        -100.5076 rho                  0.124797   Durbin-Watson        1.594644 Everything seemed correct, only the R-squared seems to have increased, whereas my intuition was that it should have decreased. A verification with Stata (8) gave me that R-squared is 0.40 (all other test-values and coefficients are the same). Does this have something to do with the way Gretl calculates R-squared for Prais-Winsten compared to Stata 8? Or is it a bug somehow..? I'd appreciate any answer! Thanks. B