  The proton, neutron and deuteron structure functions $F_2(x,Q^2)$ and
$g_1(x,Q^2)$, measured at intermediate $Q^2$, are analyzed within a Regge
approach. This analysis serves to fix the parameters of this scheme which are
then used to calculate, in a unified Regge approach, the properties of $\rho^0$
meson electroproduction on the proton and the deuteron. In this way, the
double-spin asymmetry observed at HERMES in $\rho^0$ electroproduction on the
proton, can be related to the anomalous behavior of the flavor-singlet part of
the spin-dependent structure function $g_1(x,Q^2)$ at small $x$.
