A study of Patent Thickets (1.31Mb) - UK Intellectual Property Office
A study of Patent Thickets (1.31Mb) - UK Intellectual Property Office
A study of Patent Thickets (1.31Mb) - UK Intellectual Property Office
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80 A Study <strong>of</strong> <strong>Patent</strong> <strong>Thickets</strong><br />
Proportional hazard<br />
AFT<br />
Variable Cox PH Weibull Log logistic<br />
Log (triples density in class) -0.112*** -0.112*** -0.123***<br />
(0.006) (0.006) (0.007)<br />
Log (patents in class) 0.644*** 0.645*** 0.696***<br />
(0.019) (0.017) (0.020)<br />
Log assets 0.070*** 0.045*** 0.048***<br />
(0.004) (0.005) (0.006)<br />
Industry dummies stratified# stratified# stratified#<br />
Year dummies yes yes yes<br />
Log likelihood -108,086.4 -51,393.4 -51,369.1<br />
Degrees <strong>of</strong> freedom 10 35 35<br />
Chi-squared 2676.4 2415.9 1982.1<br />
All estimates are weighted estimates, weighted by sampling probability. Coefficients shown are elasticities <strong>of</strong> the<br />
hazard w.r.t. the variable.<br />
*** (**) denote significance at the 1% (5%) level.<br />
998,219 firm-TF34 observations with 12,991 entries (29,435 firms)<br />
Time period is 2002-2009. Sample is all <strong>UK</strong> firms with nonmissing assets<br />
AFT - Accelerated Failure Time models<br />
# Estimates are stratified by industry - each industry has its own baseline hazard.<br />
Table 7.4: Hazard <strong>of</strong> entry into patenting in a TF34 Class - Comparing models
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