  The description of the energiy spectra of $0^{+}$ states for rare-earth
nuclei has been done involving the degree of the collectivity of corresponding
$0^{+}$-state as a systematics parameter. Holshtein-Primakoff representation
leads to very good agreement with experiment. Within the framework of this
approach the parameter of the collectivity is mainly determined by pairs of
particles constructed on single ''effective'' level. The results may be helpful
both for nuclear structure experimentalists and theorists in their
investigations of low-lying states structure and transition probabilities.
