  We derive the exact semiclassical expression for the second inertial
parameter $\cal B$ for the superfluid and normal phases. Interpolation between
these limiting values shows that the function ${\cal B}(I)$ changes sign at the
spin $I_c$, which is critical for a rotational spectrum. The quantity $\cal B$
turns out to be a sensitive measure of the change in static pairing
correlations. The superfluid-to-normal transition reveals itself in the
specific variation of the ratio ${\cal B}/{\cal A}$ versus spin $I$ with the
plateau characteristic of the normal phase. We find this dependence to be
universal for normal deformed and superdeformed bands. The long plateau with a
small value ${\cal B}/{\cal A}\sim A^{-8/3}$ explains the extreme regularity of
superdeformed bands.
