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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A Study <strong>of</strong> <strong>Patent</strong> <strong>Thickets</strong> 79<br />
Variable (1) (2) (3) (4) (5) (6)<br />
Log (triples density -0.112*** -0.112*** -0.119*** -0.112*** -0.119***<br />
in class) (0.006) (0.006) (0.007) (0.006) (0.007)<br />
Log (patents in class) 0.470*** 0.643*** 0.644*** 0.702*** 0.644*** 0.703***<br />
(0.017) (0.019) (0.019) (0.022) (0.019) (0.022)<br />
Log assets 0.064*** 0.064*** 0.067*** 0.072*** 0.070*** 0.075***<br />
(0.003) (0.003) (0.003) (0.004) (0.004) (0.004)<br />
Log (triples density) 0.005** 0.005**<br />
* Log assets (0.002) (0.002)<br />
Log (patents) -0.037*** -0.038***<br />
* Log assets (0.006) (0.006)<br />
Industry dummies no no yes yes stratified# stratified#<br />
Year dummies yes yes yes yes yes yes<br />
Log likelihood -145,999.7 -145,815.9 -145,773.0 -145,755.2 -108,086.4 -108,068.2<br />
Degrees <strong>of</strong> freedom 9 10 34 36 10 12<br />
Chi-squared 2293.4 2660.8 2746.7 2782.4 2676.4 2712.9<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 />
Time period is 2002-2009. Sample is all <strong>UK</strong> firms with nonmissing assets<br />
998,219 firm-TF34 observations with 12,991 entries (29,435 firms)<br />
# Estimates are stratified by industry - each industry has its own baseline hazard<br />
Table 7.3: Hazard <strong>of</strong> entry into patenting in a TF34 Class - Proportional Hazard (Cox)<br />
Model
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