(a)

(b)

(c)

(d)

dlpatent

lpatent

lpatent

lpatent

L.inde_com

0.797***

0.726***

0.726**

0.888**

(3.00)

(2.78)

(2.00)

(2.01)

L.log_Total

0.519***

0.413***

0.413***

0.416***

(31.06)

(13.81)

(7.14)

(6.83)

L.cap_exp

0.497**

0.290

0.290

0.394

(2.17)

(1.41)

(1.17)

(1.24)

L.Leverage

−0.000373***

0.000579

0.000579***

0.000664***

(−3.31)

(1.30)

(5.08)

(9.03)

L.Borad_size

0.0135

0.0175*

0.0175

0.0308*

(1.59)

(1.81)

(1.12)

(1.90)

L.logQ

0.0734***

0.0163**

0.0163*

0.0114

(4.65)

(2.27)

(1.88)

(0.93)

year_pre2003

−0.000230

−0.000226

(−1.24)

(−1.25)

_cons

−9.834***

−7.795***

−7.336***

−7.612***

(−21.14)

(−11.64)

(−5.92)

(−5.86)

N

8185

8185

8185

8185

r2

0.202

0.189

0.189

0.191

Year fixed effects

Yes

Yes

Yes

Yes

Firm fixed effects

No

Yes

Yes

Yes

Trend control

No

No

Yes

Yes

Control*bill

No

No

No

Yes