A formula has been derived which matches global redshift periodicities. Observed periodicities appear to be contained within the set of integral negative ninth roots of 2 times the speed of light. Galaxy samples from the Virgo cluster, the Perseus and Cancer supercluster regions, and local space, are examined for periodicities as viewed from the cosmic background rest frame. Numerous periodicities are present, most of which are coincident with periods given by the ninth- root rule; periodicities associated with previously postulated 72 and 36 km s^-1^ periods are especially strong. Some classes of local galaxies are also periodic in a galactocentric rest frame. The strength of specific periods depends upon galaxy type as characterized primarily by the width of the 21 cm profile. Variation of the width range shifts power between harmonics but does not induce new periods. Using a previously predicted dependence of periodicity on z and q_0_ we confirm that q_0_ is consistent with a value of 1/2.