The website used Census data relating to the distribution of ethnic groups across a given municipality (Hispanic/Latino, White, Black, and Asian/Pacific Islander).
Rocky River's overall diversity score was 5.9, for what it's worth. Lancaster, Ohio, also made the list, coming in as just slightly less diverse than River. Oh, and Green, Mentor, Ashland, Brunswick and Cuyahoga Falls all cracked the top 20, as well. OHIO!
There were more than 1,900 cities grouped into the data collection.