The other thing to keep in mind is that the numbers that are reported are based on the current contract. A home could have been on the market with 1 or 2 other agents for a much longer period of time. So in some cases the average DOM under-estimates the reality.
Lastly - does it really matter? What does this tell you as a buyer? That you can take your time? Or perhaps not? At some level it is useful, but certainly not something one should rely on for making important buying decisions.