Benchmark, matched case, or contrast pair

Compare similar cases that differ in one meaningful way to see what that difference does.

Two funds in your retirement account track the same market, hold nearly the same stocks, and cover the same years. One charges 0.65% a year, one charges 0.05%, and your advisor insists the expensive one is "actively better." You could argue about philosophy, or you could let the pairing do the work.

The move is to compare similar cases that differ in one meaningful way, so the difference in outcomes can be pinned on the difference in inputs. The cue is a claim of superiority between things that are almost twins. Steps: match the pair on everything you can (asset class, benchmark, time period), isolate the single meaningful difference (fees and active management), then compare results net of that difference over the matched window. When it works, "actively better" has to show up as extra return after fees against its near-twin, and you can see plainly whether it does. Don't use it when the cases differ in many ways at once; a contrast between a stock fund and a bond fund can't tell you which of the dozen differences produced the gap, and the comparison becomes theater.