Overview
What is it:
A modifier describes a role a metric can play in a PSU (or short-term incentive) design, as distinct from being the primary driver of payout. Primary metrics resolve first, like the values inside a math equation's parentheses, and combine to produce a base result. A modifier then acts on that result from the outside, adjusting it up or down within a capped range, rather than contributing its own value to the calculation. In formula terms, a sample structure might look like this:
Final Payout = [(Metric 1 Payout % + Metric 2 Payout %) ÷ 2] × Modifier
Metric 1 and Metric 2 are resolved independently and averaged inside the brackets; the modifier is applied only once that inner result already exists. A modifier can't create payout on its own: if the primary metrics resolve to zero, the modifier has nothing to adjust.
Why does it matter:
Knowing whether a metric contributes to the payout or only scales it lets you correctly identify what's actually driving your number. Relative Total Shareholder Return (rTSR) is a popular metric used by many companies in their formula. However, some companies use it as a primary metric and others as a modifier. Don't automatically assume it's a main driver just because it's named in your award letter.
What do people most often get wrong:
People often assume the same metric always plays the same role. Relative TSR, for example, is the dominant, primary driver at some companies and only a capped modifier at others. The mention of a metric doesn't tell you which role it's playing; only a clear reading of the plan document does.