  If there is an extra U(1) gauge symmetry broken at low energies, then it may
be possible from the charges of the known quarks and leptons under this U(1) to
make inferences about how much gauge unification occurs at high scales and
about the unification group. (For instance, there are certain observed
properties of an extra $U(1)'$ that would be inconsistent with unification in
four dimensions at high scales.) A general analysis is presented. Two criteria
used in this analysis are (1) the degree to which the generator of the extra
U(1) mixes with hypercharge, and (2) the ratio of the extra U(1) charge of the
"10" and the "$\bar{5}$" of quarks and leptons.
