Owing to the increasing availability and accessibility of national data, the last decade witnessed growing interest in identifying racial/ethnic, socioeconomic, and spatial inequalities in access to high-quality nursing homes.

However, caution is warranted when empirical studies that use overall quality rating or domain ratings from the Five-Star Quality Rating System make comparisons across state boundaries. Such studies implicitly assume that these ratings are state-invariant—that is, the same underlying construct is measured across states given a specific rating (eg, 5-star). Yet the nonlinear and state-dependent way in which these ratings are constructed violates this assumption.