  We study the Japan and U.S. patent records of several decades to demonstrate
the effect of collaboration on innovation. We find that statistically inventor
teams slightly outperform solo inventors while company teams perform equally
well as solo companies. By tracking the performance record of individual teams
we find that inventor teams' performance generally degrades with more repeat
collaborations. Though company teams' performance displays strongly bursty
behavior, long-term collaboration does not significantly help innovation at
all. To systematically study the effect of repeat collaboration, we define the
repeat collaboration number of a team as the average number of collaborations
over all the teammate pairs. We find that mild repeat collaboration improves
the performance of Japanese inventor teams and U.S. company teams. Yet,
excessive repeat collaboration does not significantly help innovation at both
the inventor and company levels in both countries. To control for unobserved
heterogeneity, we perform a detailed regression analysis and the results are
consistent with our simple observations. The presented results reveal the
intricate effect of collaboration on innovation, which may also be observed in
other creative projects.
