While I do have some experience, that's not really that relevant. I'm not saying this because of my own experience (which would be anecdotal evidence). It's based on actual market data, which is what is actually important for making a generalization like this. Many statistics show that overwhelmingly, active investors underperform indexes. And that is especially true year over year because a lot more people can get lucky a few times but they cannot consistently reproduce those results.
One example of some data that shows this is the SPIVA score cards. Here's a nice page that explains it and presents some of the recent results: https://www.bogleheads.org/wiki/SPIVA_scorecards
There is tons of other information if you just Google for it. When it comes to actual evidence of performance, the facts are pretty clear!
How about you? Do you have any objective data to show otherwise?
