accuracy of the reddening and metallicity corrections applied to the Cepheids, and biases introduced by crowding and the magnitude limit of the sample. When added in quadrature, as in Freedman [[et al. ]{}]{}(2001), these effects introduce a 9% systematic uncertainty in the galaxy distances. This corresponds to a difference $\Delta_{\rm III} = \pm 0.037$ in $\log(M/L)$. This uncertainty must be taken into account, e.g., when comparing the $M/L$ values of local galaxies to the predictions of stellar population synthesis models.

The systematic Cepheid distance scale uncertainties listed in the previous paragraph do [*not*]{} affect a relative comparison of $M/L$ values of nearby and distant galaxies. Any shift in the overall distance scale of the Universe would affect both types of galaxies equally, and would therefore cancel out when evaluating a difference in $\log(M/L)$. The only distance scale uncertainties that do affect such a comparison are those that impact the estimate of $H_0$, but not the Cepheid distances to local galaxies. These uncertainties have both a systematic and a random component. The systematic component is due to cosmic variance, i.e., the effect that local samples of galaxies may yield an estimate of $H_0$ that differs from the true cosmic value as 