{"term":{"id":"15034","title":"Simpson’s diversity index","longtitle":"IUPAC Gold Book - Simpson’s diversity index","doi":"10.1351\/goldbook.15034","code":"15034","status":"current","definitions":[{"id":1,"text":"Dominance index weighted toward the abundance of the most common species, giving the probability of any two individuals drawn at random from an infinitely large community belonging to different species. The bias corrected mathematical form of Simpson’s index is \\[D = \\sum \\limits_{i=1}^{S} p_{i}^{2}\\] where \\(p_{i}\\) is the fraction of all organisms which belong to the \\(i\\)-th species and \\(S\\) is the number of species.","notes":{"1":"Since \\(D\\) and diversity are negatively related, Simpson’s index is usually expressed as either a reciprocal or a complementary form (\\(1\/D\\) or \\(1 - D\\)) so that as the index goes up, so does measure of diversity."},"links":[{"term":"community","url":"https:\/\/goldbook.iupac.org\/terms\/view\/14531"},{"term":"diversity index","url":"https:\/\/goldbook.iupac.org\/terms\/view\/14599"}],"sources":["PAC, 2009, 81, 829. 'Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)' on page 945 (https:\/\/doi.org\/10.1351\/PAC-REC-08-07-09)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/15034\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/15034\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/15034\/plain"},"citation":"Citation: 'Simpson’s diversity index' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.15034","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-07-23T16:02:16+00:00"}}