{"license":"https://creativecommons.org/licenses/by/4.0/","dataset":"reports","count":1,"filters":{"report":"hhi-primer","reportMatched":true,"reportId":"rep-hhi-primer","reportSlug":"hhi-primer","reportTitle":"How HHI Helps Explain Market Concentration"},"rows":[{"id":"rep-hhi-primer","slug":"hhi-primer","title":"How HHI Helps Explain Market Concentration","subtitle":"A public primer for reading concentration dashboards","summary":"An open explainer on HHI, CR4, effective number of firms, and why source coverage matters.","body":"HHI is the sum of squared market shares. It is useful because it gives larger firms more weight, but it is not a legal conclusion. This observatory reports HHI only when public sources provide enough reliable shares or when a public agency reports the metric directly. Market definition, geography, vintage, and missing firms can change interpretation. The mobile wireless profile uses FCC-reported HHI, while search and browser profiles use public usage-share tables with clear limitations.","coverImageUrl":null,"publishedAt":"2026-05-16","relatedMarketIds":["mkt-wireless","mkt-search","mkt-browser"],"sourceIds":["fcc-2024-cmr","statcounter-search-us-2026","statcounter-browser-us-2026"],"sourceBasis":"FCC source-reported HHI and StatCounter public usage-share tables.","tableOfContents":["What HHI measures","Where CR4 helps","Why source notes matter"],"preview":"A short public-interest guide to reading descriptive concentration metrics.","publicationType":"methodology_primer","seriesTitle":"Methods and Measures","seriesNumber":"AR-MM-2026-01","authorName":"Antitrust Radar Research Team","version":"1.0","updatedAt":"2026-05-16","publicationStatus":"current","revisionNote":"Initial public edition.","canonicalCitation":"Antitrust Radar Research Team. (2026, May 16). How HHI Helps Explain Market Concentration: A public primer for reading concentration dashboards. Methods and Measures, AR-MM-2026-01 (Version 1.0). Antitrust Radar. https://antitrustradar.org/reports/hhi-primer","citationDownloads":{"bibtex":"/reports/hhi-primer/citation/bibtex","ris":"/reports/hhi-primer/citation/ris"},"sourceProfileHrefs":["/sources/fcc-2024-cmr","/sources/statcounter-search-us-2026","/sources/statcounter-browser-us-2026"]}]}