  The global mass dependence of the nuclear symmetry energy and its two basic
ingredients due to the mean-level spacing and effective strength of the
isovector mean-potential is studied within the Skyrme-Hartree-Fock model. In
particular, our study determines the ratio of the surface-to-volume
contributions to the nuclear symmetry energy to be ~1.6 and reveals that
contributions due to mean-level spacing and effective strength of the isovector
mean-potential are almost equal after removing momentum-dependent effects by
rescaling them with isoscalar and isovector effective masses, respectively.
