I wonder if there's also a marginal effect here where early on each paper is contributing a lot to your knowledge base, but as time goes on the marginal contrib

I wonder if there's also a marginal effect here where early on each paper is contributing a lot to your knowledge base, but as time goes on the marginal contribution reduces. I haven't done a PhD (yet), but I get the sense that in the early years you spend a lot of time under water trying to swim.