******************* Results from STATA regressions are reported below ******************* . generate logwage=log(wage) . regress logwage sibs Source | SS df MS Number of obs = 935 -------------+------------------------------ F( 1, 933) = 22.31 Model | 3.86818074 1 3.86818074 Prob > F = 0.0000 Residual | 161.788103 933 .173406326 R-squared = 0.0234 -------------+------------------------------ Adj R-squared = 0.0223 Total | 165.656283 934 .177362188 Root MSE = .41642 ------------------------------------------------------------------------------ logwage | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- sibs | -.0279044 .0059082 -4.72 0.000 -.0394992 -.0163096 _cons | 6.861076 .0220776 310.77 0.000 6.817748 6.904403 ------------------------------------------------------------------------------ . regress educ brthord Source | SS df MS Number of obs = 852 -------------+------------------------------ F( 1, 850) = 37.29 Model | 173.087012 1 173.087012 Prob > F = 0.0000 Residual | 3945.88364 850 4.64221605 R-squared = 0.0420 -------------+------------------------------ Adj R-squared = 0.0409 Total | 4118.97066 851 4.84015353 Root MSE = 2.1546 ------------------------------------------------------------------------------ educ | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- brthord | -.2826441 .0462882 -6.11 0.000 -.3734967 -.1917915 _cons | 14.14945 .1286754 109.96 0.000 13.89689 14.40201 ------------------------------------------------------------------------------ . end of do-file . ivreg logwage (educ = brthord) Instrumental variables (2SLS) regression Source | SS df MS Number of obs = 852 -------------+------------------------------ F( 1, 850) = 16.63 Model | -4.20185534 1 -4.20185534 Prob > F = 0.0000 Residual | 151.01792 850 .177668141 R-squared = . -------------+------------------------------ Adj R-squared = . Total | 146.816065 851 .172521815 Root MSE = .42151 ------------------------------------------------------------------------------ logwage | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- educ | .1306448 .0320385 4.08 0.000 .0677609 .1935287 _cons | 5.030397 .432949 11.62 0.000 4.180622 5.880171 ------------------------------------------------------------------------------ Instrumented: educ Instruments: brthord ------------------------------------------------------------------------------ . ivreg logwage (educ = sibs) Instrumental variables (2SLS) regression Source | SS df MS Number of obs = 935 -------------+------------------------------ F( 1, 933) = 21.59 Model | -1.51973315 1 -1.51973315 Prob > F = 0.0000 Residual | 167.176016 933 .179181154 R-squared = . -------------+------------------------------ Adj R-squared = . Total | 165.656283 934 .177362188 Root MSE = .4233 ------------------------------------------------------------------------------ logwage | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- educ | .1224326 .0263506 4.65 0.000 .0707194 .1741459 _cons | 5.130026 .3551712 14.44 0.000 4.432999 5.827053 ------------------------------------------------------------------------------ Instrumented: educ Instruments: sibs ------------------------------------------------------------------------------ . regress educ sibs brthord Source | SS df MS Number of obs = 852 -------------+------------------------------ F( 2, 849) = 26.29 Model | 240.246365 2 120.123183 Prob > F = 0.0000 Residual | 3878.72429 849 4.56857985 R-squared = 0.0583 -------------+------------------------------ Adj R-squared = 0.0561 Total | 4118.97066 851 4.84015353 Root MSE = 2.1374 ------------------------------------------------------------------------------ educ | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- sibs | -.1528673 .0398705 -3.83 0.000 -.2311236 -.0746109 brthord | -.1526742 .0570764 -2.67 0.008 -.2647017 -.0406467 _cons | 14.2965 .1332881 107.26 0.000 14.03489 14.55811 ------------------------------------------------------------------------------ . ivreg logwage exper tenure black (educ = sibs) Instrumental variables (2SLS) regression Source | SS df MS Number of obs = 935 -------------+------------------------------ F( 4, 930) = 24.92 Model | 27.9196953 4 6.97992381 Prob > F = 0.0000 Residual | 137.736588 930 .148103858 R-squared = 0.1685 -------------+------------------------------ Adj R-squared = 0.1650 Total | 165.656283 934 .177362188 Root MSE = .38484 ------------------------------------------------------------------------------ logwage | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- educ | .0936325 .0337194 2.78 0.006 .0274576 .1598074 exper | .0209216 .0083877 2.49 0.013 .0044605 .0373827 tenure | .0115482 .0027397 4.22 0.000 .0061716 .0169248 black | -.1833285 .0501358 -3.66 0.000 -.281721 -.0849361 _cons | 5.215976 .5434515 9.60 0.000 4.149443 6.282509 ------------------------------------------------------------------------------ Instrumented: educ Instruments: exper tenure black sibs ------------------------------------------------------------------------------ . regress educ sibs exper tenure black Source | SS df MS Number of obs = 935 -------------+------------------------------ F( 4, 930) = 83.48 Model | 1190.65488 4 297.66372 Prob > F = 0.0000 Residual | 3316.16437 930 3.56576814 R-squared = 0.2642 -------------+------------------------------ Adj R-squared = 0.2610 Total | 4506.81925 934 4.82528828 Root MSE = 1.8883 ------------------------------------------------------------------------------ educ | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- sibs | -.1703301 .0281815 -6.04 0.000 -.2256368 -.1150233 exper | -.2276516 .0146296 -15.56 0.000 -.2563625 -.1989407 tenure | .0259141 .0126151 2.05 0.040 .0011568 .0506715 black | -.6226722 .1946812 -3.20 0.001 -1.004738 -.2406069 _cons | 16.49435 .1951037 84.54 0.000 16.11145 16.87724 ------------------------------------------------------------------------------ . predict yhat (option xb assumed; fitted values) . regress logwage yhat exper tenure black Source | SS df MS Number of obs = 935 -------------+------------------------------ F( 4, 930) = 22.75 Model | 14.7631567 4 3.69078917 Prob > F = 0.0000 Residual | 150.893127 930 .162250674 R-squared = 0.0891 -------------+------------------------------ Adj R-squared = 0.0852 Total | 165.656283 934 .177362188 Root MSE = .4028 ------------------------------------------------------------------------------ logwage | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- yhat | .0936325 .0352931 2.65 0.008 .0243691 .1628959 exper | .0209216 .0087792 2.38 0.017 .0036923 .0381509 tenure | .0115482 .0028675 4.03 0.000 .0059206 .0171757 black | -.1833285 .0524757 -3.49 0.000 -.286313 -.080344 _cons | 5.215976 .5688147 9.17 0.000 4.099667 6.332285 ------------------------------------------------------------------------------ . log close