  We investigate whether the hypercharge assignments in the Standard Model can
be interpreted as a hint at Grand Unification in the context of heterotic
string theory. To this end, we introduce a general method to calculate U(1)_Y
for any heterotic orbifold and compare our findings to the cases where
hypercharge arises from a GUT. Surprisingly, in the overwhelming majority of
3-2 Standard Models, a non-anomalous hypercharge direction can be defined, for
which the spectrum is vector-like. For these models, we calculate sin^2 theta
to see how well it agrees with the standard GUT value. We find that 12% have
sin^2 theta = 3/8, while all others have values which are less. Finally, 89% of
the models with sin^2 theta = 3/8 have U(1)_Y in SU(5).
