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Table 3 Estimates of OLS-Pool and Two-Step Difference GMM models

From: Physician induced demand for knee replacement surgery in Iran

Independent Variables OLS-Pool Two-Step Difference GMM
\(\dot{{\mathbf{y}}_{\mathbf{it}}}=\dot{{\mathbf{n}}_{\mathbf{it}}}\)
(1)
\(\dot{{\mathbf{y}}_{\mathbf{it}}}=\dot{{\mathbf{s}}_{\mathbf{it}}}\)
(2)
\(\dot{{\mathbf{y}}_{\mathbf{it}}}=\dot{{\mathbf{f}}_{\mathbf{it}}}\)
(3)
\(\dot{{\mathbf{y}}_{\mathbf{it}}}=\dot{{\mathbf{n}}_{\mathbf{it}}}\)
(4)
\(\dot{{\mathbf{y}}_{\mathbf{it}}}=\dot{{\mathbf{s}}_{\mathbf{it}}}\)
(5)
\(\dot{{\mathbf{y}}_{\mathbf{it}}}=\dot{{\mathbf{f}}_{\mathbf{it}}}\)
(6)
\(\dot{{\mathrm{d}}_{\mathrm{it}}}\))SE( 0.71a (0.03) 0.79a (0.03) 0.07 (0.01) 0.94a (0.05) 1.01aa (0.04) 0.06a (0.02)
\(\dot{{\mathrm{y}}_{\mathrm{it}-1}}\) )SE( 0.63a (0.02) 0.63a (0.02) 0.68a (0.03) -0.04a (0.05) 0.07a (0.03) 0.11a (0.05)
\(\dot{\mathrm{inc}\ }\))SE( 0.15 (0.08) 0.09a (0.07) -0.04 (0.02) -1.25 (1.88) 0.80 (0.33) 0.54 (0.35)
Constant 7.96a (1.51) 13.06a (1.69) 4.35a (0.85) 36.18a (32.56) 11.85a (10.96) 0.84a (5.94)
N. observation 823 823 823 823 823 823
R-squared 0.826 0.805 0.473    
F-test (p-value)     0.000 0.000 0.036
Wald test     601.34 599.96 8.55
Hansen test     0.361 0.284 0.413
Sargan test     0.277 0.175 0.339
M2 test     0.671 0.589 0.712
  1. aIndicate that the coefficients are significant at the 1% level