(1)

(2)

(3)

混合回归

固定效应模型

随机效应模型

log_all

0.0000305^***

0.000000800^***

0.0000231^***

(0.34)

(0.01)

(0.26)

patent

0.0548^***

0.0548^***

0.0548^***

(296.03)

(297.38)

(296.64)

RD

0.00703^***

0.00723^***

0.00710^***

(37.64)

(36.93)

(37.41)

_cons

0.125^***

0.129^***

0.126^***

(39.97)

(39.25)

(39.75)

N

1269

1269

1269

R²

0.989

0.988

F

36577.6

35433.6