  Measuring changes in overall inequality between different educational groups
is often performed by quantifying variations in educational marital homophily
across consecutive generations. However, this task becomes challenging when the
education level of marriageable individuals is generation-specific. To address
this challenge, various indicators have been proposed in the assortative mating
literature.
  In this paper, we review a set of criteria that indicators must satisfy to be
considered as suitable measures of homophily and inequality. Our analytical
criteria include robustness to the number of educational categories
distinguished and the negative association between intergenerational mobility
and homophily. Additionally, we also impose an empirical criterion on the
identified qualitative historical trend in homophily between 1960 and 2010 in
the US at the national and sub-national levels.
  Our analysis reveals that while a specific cardinal indicator meets all three
criteria, many commonly applied indices do not. We propose the application of
this well-performing indicator to quantify the trend in overall inequality in
any country, including European countries, with available population data on
couples' education level.
