  We focused on how repeat collaborations in projects for inventions affect
performance. Repeat collaborations have two contradictory aspects. A positive
aspect is team development or experience, and a negative aspect is team
degeneration or decline. Since both contradicting phenomena are observed,
inventors have a dilemma as to whether they should keep collaborating in a team
or not. The dilemma has not previously been quantitatively analyzed.
  We provide quantitative and extensive analyses of the dilemma in creative
projects by using patent data from Japan and the United States. We confirm
three predictions to quantitatively validate the existence of the dilemma. The
first prediction is that the greater the patent a team achieves, the longer the
team will work together. The second prediction is that the impact of
consecutive patents decreases after a team makes a remarkable invention, which
is measured by the impact of patents. The third prediction is that the
expectation of impact with new teams is greater than that with the same teams
successful in the past. We find these predictions are validated in patents
published in Japan and the United States. On the basis of these three
predictions, we can quantitatively validate the dilemma in creative projects.
We also propose preventive strategies for degeneration. One is developing
technological diversity, and another is developing inventor diversity in
teams.We find the two strategies are both effective by validating with the
data.
