At the level you're talking about, it sounds like you should use similar metrics those managers use. Revenue/expense of the systems they oversee or business value of initiatives under your purview.

Not that that would be useful for anyone. Managers will get away with saying they "grew revenue by $10 million per year" or "reduced expenses by 20%" despite that being mostly BS unconnected with their actions or choices. I don't see why you couldn't get the same level of credit.