  The superconformal group of N=4 super-Yang-Mills has two types of operator
representations: short and long. We conjecture that operator product expansions
for which at least two of the three operators are short exactly respect a bonus
U(1)_Y R-symmetry, which acts as an automorphism of the superconformal group.
This conjecture is for arbitrary gauge group G and gauge coupling g_{YM}. A
consequence is that n\leq 4-point functions involving only short operators
exactly respect the U(1)_Y symmetry, as has been previously conjectured based
on AdS duality. This, in turn, would imply that all n\leq 3 -point functions
involving only short operators are not renormalized, as has also been
previously conjectured and subjected to perturbative checks. It is argued that
instantons are compatible with our conjecture. Some perturbative checks of the
conjecture are presented and SL(2,Z) modular transformation properties are
discussed.
