"They usually are. The 20% is typically measured against a benchmark. "
That is incorrect. The 20% refers to a fund management performance fee equal to 20% of all profits (without reference to any benchmark index). However, there is usually a "hurdle rate," like 5%, so 20% refers to 20% of all profits above the hurdle rate. There is also a "high water mark," so that past losses are counted against any "profits" to which the performance fee is applied.
That is incorrect. The 20% refers to a fund management performance fee equal to 20% of all profits (without reference to any benchmark index). However, there is usually a "hurdle rate," like 5%, so 20% refers to 20% of all profits above the hurdle rate. There is also a "high water mark," so that past losses are counted against any "profits" to which the performance fee is applied.