Why Are Oak Leaves So Big?

Q: I found an enormous oak leaf in my yard cleanup. I regularly have hand-sized leaves but never one this large. Why are some oak leaves so big? 

A: Shaded leaves tend to be larger than sun-exposed leaves. Is the tree in the shade? Could it be that this was a leaf from the inner canopy? Young, excessively vigorous trees (or vigorous shoots on mature trees) tend to produce bigger leaves. First and second-year acorn sprouts also make large leaves, more effectively with their larger siblings.