Hi I have been struggling to choose the right covariates for matching and the following (kernel density distribution of propensity score and matching result) is the outcome.
I was wondering if I could still use these variables for regression such as difference and differences with variables that suffer from imbalance after matching.
With these variables, diff-in-diff regression may suffer from biased estimates?
Any tip or suggestion for improving the analysis outcome would be much appreciated.
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I was wondering if I could still use these variables for regression such as difference and differences with variables that suffer from imbalance after matching.
With these variables, diff-in-diff regression may suffer from biased estimates?
Any tip or suggestion for improving the analysis outcome would be much appreciated.
Code:
pstest der roi ebit hhi_sales lnl lnk ksic2c, both ---------------------------------------------------------------------------------------- Unmatched | Mean %reduct | t-test | V(T)/ Variable Matched | Treated Control %bias |bias| | t p>|t| | V(C) --------------------------+----------------------------------+---------------+---------- der U | 278.12 198.33 5.9 | 1.73 0.084 | 0.27* M | 251.17 364.17 -8.3 -41.6 | -0.98 0.328 | 0.08* | | | roi U | .03556 .04006 -4.9 | -1.69 0.092 | 0.95 M | .03398 .03154 2.7 45.8 | 0.61 0.542 | 1.31* | | | ebit U | 2.6e+11 3.6e+10 37.4 | 19.11 0.000 | 12.88* M | 1.9e+11 1.8e+11 1.3 96.5 | 0.28 0.779 | 1.23* | | | hhi_sales U | .2943 .24938 21.8 | 7.57 0.000 | 1.05 M | .28274 .27715 2.7 87.6 | 0.54 0.586 | 0.67* | | | lnl U | 7.8331 6.1254 148.0 | 53.98 0.000 | 1.41* M | 7.3532 7.4134 -5.2 96.5 | -1.15 0.250 | 0.92 | | | lnk U | 26.683 24.625 130.4 | 48.53 0.000 | 1.59* M | 26.148 26.122 1.7 98.7 | 0.34 0.737 | 0.94 | | | sectors U | 38.882 30.204 48.1 | 17.06 0.000 | 1.20* M | 36.116 37.686 -8.7 81.9 | -1.71 0.088 | 0.68* | | | ---------------------------------------------------------------------------------------- * if variance ratio outside [0.90; 1.11] for U and [0.88; 1.14] for M ----------------------------------------------------------------------------------- Sample | Ps R2 LR chi2 p>chi2 MeanBias MedBias B R %Var -----------+----------------------------------------------------------------------- Unmatched | 0.316 2391.26 0.000 56.7 37.4 160.8* 1.32 71 Matched | 0.003 8.68 0.192 4.4 2.7 13.3 0.56 71 ----------------------------------------------------------------------------------- * if B>25%, R outside [0.5; 2]