I was listening to an old Hidden Brain podcast that made reference to the phenomena of overclaiming: that if you ask collaborators what percentage of the work they do, that total comes to over 100%, which is mathematically impossible. The point to the episode is the usual one, that we need to recognize we're probably over-stating our impact and under-valuing others, and need to check that bias. (About minute 23 here, if you care.)
First of all, that's true: we do all over-emphasize our work, because we did it, viscerally; we either didn't even see, or saw but didn't feel, the contributions of others, so the natural tendency is to under-weight them. Got it. But also... that isn't how collaboration works.
That percentage-contribution idea might be how execution works, sort of, if there's a list of things to do and we can count how many we each did and how easy or hard those items were as a percentage of total work. But that subtask execution is only a piece of good collaboration. Good collaboration requires shared ownership, and there isn't a good way to allot credit for that except by giving joint credit.
As an example, in a recent meeting a teammate mused that something-or-other would be great if only we could do it, I agreed by said that the problem was this-and-such, so we'd need this to be able to, and between the two of us and a suggestion from a third we discovered with might have a solution. Who "did" that? We all did; without any of us, the idea wouldn't have come together. Or I had a colleague who was doing the work on something and had gotten stuck; I made a suggestion for what to do on that roadblock. I didn't "do the work," they did---but it wouldn't have happened on time without my suggestion, and the plan they were working from was mine (but with review and input from others), so I want some credit also.
If you're in an environment in which credit is being apportioned at all, then I argue you're in a toxic mindset, and need to break that mindset. It's a common joke that leadership is going to "take credit for" their employees work---but they should, and it should be a both/and concept of credit. For that matter, in my career I have several times had the role of fielding all the inbound distractions---bug reports, oncall pages, support queries, whatever---to let the team focus on "the important thing." If an engineer takes on that role of sponging up "everything else" so the team can deliver the crucial thing, that teammate made the crucial delivery happen. So did the ones people the feature work, of course, but the impact can be both/and.
First, this is how good leadership should work and be evaluated: the engineers get credit for doing what they do, and the leads get credit for the team's delivery, and the other teammates do also. It's perfectly appropriate to brag in your performance evaluations about how you're responsible for the team's successful work, and you have to call out who did what so they get their credit also; the shout-out doesn't diminish your leadership impact but enhances it.
Second, this is how good culture works. If you can't build a culture in which collective delivery begets widespread individual credit, then you are building a culture in which people have an incentive to be selfish about their own perspectives, which leads to selfish decisions about time and effort. If you instead build a culture about collective delivery, you build a culture about collaborative support. And in that worldview, you do need a way to ensure that performance reviews and eventually raises include valuing that kind of teamwork. There is still going to be a need to evaluate individual performance, obviously, and a way to catch an underperformer being carried by the collective team; those cases need to be noted and managed. But the mechanism shouldn't be bean-counting the amount of direct contribution without also acknowledging the role of indirect and of shared contributions.
