...occurs when two or more competitors are frequently matched against one another.
When one develops an advantage, the others develop counter moves. The overall result is that the whole group becomes continuously better.
Continue this through several generations of improvement and the whole group has a marked advantage over others who started at the same baseline and didn’t get better.
When I was younger, the ratchet effect was a key component of sports excellence. Now I see it working in technical and social skills development.
Improvement seldom occurs in isolation.