I think we need more thorough analysis. Are the denied claims denied in error? The appeals success rate probably indicates that most of the appealed denied claims were denied in error... but appealed claims are a biased sample of denied claims, so it doesn't tell us much about the overall denied claims.

In my experience, I've seen some denied claims, because the provider submitted a wrong code. Then the provider submits a new claim with the correct code and it goes through.

Given the proliferation of plans, and their sometimes conflicting requirements on medicial coding, I could see that being a big driver of denials increasing over time. As well as a driver of increased administrative costs for providers and insurance companies.