Annu. Rev. Astron. Astrophys. 1998. 36: 17-55 Copyright © 1998 by Annual Reviews. All rights reserved

3.3. Summary

The mild differences between the results for H₀ quoted in this section are due to differences in the numbers of calibrators that are used and in the ways that they are matched to Hubble-flow SNe Ia. Different people would assign different relative weights to these analyses. In principle, the analyses that try to take diversity into account are preferred, but at present, some of these can use only a small number of calibrators. Suffice it to say that present Cepheid calibrations of SNe Ia give values of H₀ near 60. Mild revision is to be expected as more Cepheid-calibrated and Hubble-flow SNe Ia become available, as the zero-points of the Cepheid P - L relations are revised, and as a Cepheid metallicity dependence is taken into account if needed.