  We give an overview of our current/future analytical and numerical work on
the spin polarization in high-energy electron storage rings. Our goal is to
study the possibility of polarization for the CEPC and FCC-ee. Our work is
based on the so-called Bloch equation for the polarization density introduced
by Derbenev and Kondratenko in 1975. We also give an outline of the standard
approach, the latter being based on the Derbenev-Kondratenko formulas.
