Gauge coupling unification

Hello,

we often hear as an argument in favor of SUSY that gauge couplings do
not unify very well in the SM.
I was wondering what are the uncertainties on this measurement made in
the case of SM. Is it more experimental data related or theory
related ? Because it seems to me that the lever arm between GUT scale
(10^16 GeV) and data (10^2 GeV) is huge which leave lot of room for a
small systematic error to become big !
If one of you know a good paper on this subject, could he point me to
it ?

Thanks,
R.

.

Loading