VARIABLES

模型4

模型5

模型6

patent

patent

patent

roa

2.247^***

2.196^***

2.133^***

(2.82)

(2.76)

(2.68)

fix

−0.188

−0.192

−0.195

(−1.40)

(−1.43)

(−1.46)

size

0.546^***

0.543^***

0.541^***

(10.18)

(10.18)

(10.16)

age

−0.002

−0.017

−0.042

(−0.01)

(−0.13)

(−0.32)

lev

0.205

0.244

0.284

(0.74)

(0.88)

(1.03)

dirnum

0.311

0.310

0.341

(0.99)

(0.99)

(1.09)

inddir

2.338^***

2.364^***

2.334^***

(2.59)

(2.62)

(2.59)

inc

0.205^*

0.175

(1.83)

(1.55)

HHI_C

−2.154^*

(−1.83)

incHHI_C

1.773

(0.89)

Constant

−10.846^***

−10.944^***

−10.755^***

(−8.33)

(−8.45)

(−8.29)

Observations

741

741

741

Number of code

362

362

362

R2

0.096

0.0883

0.0955

Wald chi2

190.23

196.39

202.53

Company FE

YES

YES

YES

Year FE

YES

YES

YES