DO PATENT POOLS ENCOURAGE INNOVATION? EVIDENCE ...

while grant-backs and the presence of international members have no statistically
significant effects. Historical court records indicate that fourteen pools restricted
licensing, which is likely to have limited the potential for cumulative innovation
(e.g., Moser and Voena, 2011), and ten pools actively prevented the entry of
competitors.
I. DATA
The main data for this study consist of 472,303 applications for U.S.
patents in 103 main classes that include at least one pool patent for a pool that
formed between 1930 and 1938. The unit of analysis is the number of patent
applications per subclass and year. Twenty pools covered a total of 597 patents in
371 subclasses and 103 main classes; 45,546 subclasses in these main classes that
that do not include a pool patent serve as the control.
A. Pooled patents in 20 industries
In the first step of the data collection, we collected all mentions of patent
pools from Vaughan (1956), Gilbert (2004), and Lerner, Tirole and Strojwas
(2007) and searched the records of the National Archives in Chicago, Kansas
City, New York, and Riverside for lists of patents that formed each of these pools.
Patents for 15 pools were listed in consent decrees, which required the pools to
license their patents to outside firms. 7
Patents for three pools were listed in
7 A consent decree is granted by a court in place of a decision and based on an agreement already
reached between the government and a defendant; it generally presents the minmum, which the
Department of Justice is willing to accept in Lieur of a court decision (Vaughan 1956, p. 47)
8