  We report on an update (2021) of a phenomenological model for inelastic
neutrino- and electron-nucleon scattering cross sections using effective
leading order parton distribution functions with a new scaling variable
$\xi_w$. Non-perturbative effects are well described using the $\xi_w$ scaling
variable in combination with multiplicative $K$ factors at low $Q^2$. The model
describes all inelastic charged-lepton-nucleon scattering data
(HERA/NMC/BCDMS/SLAC/JLab) ranging from very high $Q^2$ to very low $Q^2$ and
down to the $Q^2=0$ photo-production region. The model has been developed to be
used in analyses of neutrino oscillation experiments in the few GeV region. The
2021 update accounts for the difference between axial and vector structure
functions which brings it into much better agreement with neutrino-nucleon
total cross section measurements. The model has been developed primarily for
hadronic final state masses $W$ above 1.8 GeV. However with additional
parameters the model also describes the $average$ neutrino cross sections in
the resonance region down to $W$=1.4 GeV.
