  We perform the isospin decomposition of proton and neutron SLAC data in the
region $0.01 \leq x \leq 0.1$. The isovector part is well described by a power
behaviour $x^{\alpha}$, where $\alpha$ leads to the validity of Bjorken sum
rule and it is consistent with the power extracted from all previous data using
NLO evolution. The isoscalar part behaviour may be interpreted as a partial
cancellation between a positive non-singlet contribution and a singlet one
strongly negative.
