@nechets
This is actually an important point. There’s several reasons. First of all, remember that a benchmark is specified in advance. Therefore when you’re analysing performance, you’re analysing it against the set benchmark. Scenario:
Bob invests in the market on your behalf. Your default benchmark for Bob is Total US Market. He does analysis, and decides smallcaps are the way to go this year, and buys a bunch of stocks, all smallcaps. Returns come out like this:
US Market: 10%
US smallCap: 15%
Bob: 16%
What’s the result here? Well, Bob outperformed your benchmark (Total US Market) by 6%.
“Wait, he only bought small-caps, shouldn’t he be measured against the smallcap index? In that case, didn’t he only beat it by 1%?” No. Remember, benchmark is specified in advance. His analysis showed smallcaps will outperform, so he bought them. He should be rewarded for that. Bob’s benchmark may be smallcaps, but the investor never put any such restriction. Investor just said, “go beat the US Market for me”. Bob did.