  In the past few years, a lot of evidences have been accumulated, which
indicate that the gluon polarization inside the nucleon is likely to be small
at least at the low renormalization scales. On the other hand, the recent
lattice QCD analyses suggest that the net orbital angular momentum carried by
the quarks is nearly zero. There is also some indication noticed by Brodsky and
Gardner based on the COMPASS observation of small single-spin asymmetry on the
isoscalar deuteron target, that the gluon orbital angular momentum inside the
nucleon is likely to be small. Naively combining all these observations, we are
led to a rather embarrassing conclusion that the nucleon constituents
altogether do not carry enough amount of angular momentum saturating the total
nucleon spin. We show that this somewhat confused state of affairs can be
cleared up only by paying careful attention to the scale dependencies of the
nucleon spin decomposition.
