Measuring assortative matching (AM) in marriage markets remains unsettled. Aggregate measures mask heterogeneity across groups, and changing marginal distributions hinder comparisons over time. To address these challenges, we propose an axiomatic framework for type-specific AM measures. Our preferred measure, the Average Homogamy Share, averages male and female homogamy rates. We then derive aggregate measures and extend our axiomatic framework to aggregate indices. Using US data, we document rising AM among highly educated individuals and declining AM among low-educated groups, while racial AM remains high. Positive AM has increased among low-educated and White individuals, suggesting growing segregation along both dimensions.