DO PATENT POOLS ENCOURAGE INNOVATION? EVIDENCE ...

TABLE 12: GEOGRAPHIC SCOPE
OLS– DEPENDENT VARIABLE IS PATENTS PER SUBCLASS AND YEAR
All Patents
Pool
Subclasses
Only
Cited
Patents
Only
Fixedeffects
Poisson
(1) (2) (3) (4)
Pool*pool patents -0.389** -0.478** -0.449** -0.231** -0.152**
(0.100) (0.120) (0.123) (0.063) (0.034)
Pool*pool patents*international 0.132 0.074 0.068 0.174 0.088*
(0.232) (0.215) (0.218) (0.103) (0.037)
Constant 0.947** 0.947** 2.003** 0.457**
(0.008) (0.008) (0.090) (0.005)
Subclass fixed effects Yes Yes Yes Yes Yes
Year fixed effects Yes Yes Yes Yes Yes
Linear and quadratic trends - Yes Yes Yes Yes
Standard errors clustered at the subclass level; ** significant at 1 percent, * significant at 5 percent.
Observations 1285676 1285676 25340 1,285,676
R-squared 0.526 0.526 0.528 0.497
Notes: Data include 45,917 subclasses in 103 main classes that include at least one pool patent. The timing of
invention is measured by the year of the patent application. The variable pool equals 1 for years after the pool
forms. Pool patents counts patents that were included in the initial pooling agreement and list subclass c as
primary (original) subclass. Cross-reference patents counts patents that list subclass c as a secondary (crossreference)
subclass. Pool subclass equals 1 for 371 subclasses that include at least one pool patent; crossreference
subclass equals 1 for 534 subclasses that include at least one cross-reference patent. Column (3)
restricts the data set to subclasses that are listed either as primary or secondary (cross-reference) subclass for
patents that were included in the initial pool agreement. Cited patents restricts the data set to 298,503 of 472,303
patents that are cited by at least one U.S. patent between 1920 and 2002.
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