{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,4]],"date-time":"2026-04-04T21:29:53Z","timestamp":1775338193474,"version":"3.50.1"},"reference-count":25,"publisher":"Proceedings of the National Academy of Sciences","issue":"52","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2010,12,28]]},"abstract":"<jats:p>We investigate the extent to which social ties between people can be inferred from co-occurrence in time and space: Given that two people have been in approximately the same geographic locale at approximately the same time, on multiple occasions, how likely are they to know each other? Furthermore, how does this likelihood depend on the spatial and temporal proximity of the co-occurrences? Such issues arise in data originating in both online and offline domains as well as settings that capture interfaces between online and offline behavior. Here we develop a framework for quantifying the answers to such questions, and we apply this framework to publicly available data from a social media site, finding that even a very small number of co-occurrences can result in a high empirical likelihood of a social tie. We then present probabilistic models showing how such large probabilities can arise from a natural model of proximity and co-occurrence in the presence of social ties. In addition to providing a method for establishing some of the first quantifiable estimates of these measures, our findings have potential privacy implications, particularly for the ways in which social structures can be inferred from public online records that capture individuals\u2019 physical locations over time.<\/jats:p>","DOI":"10.1073\/pnas.1006155107","type":"journal-article","created":{"date-parts":[[2010,12,9]],"date-time":"2010-12-09T04:21:33Z","timestamp":1291868493000},"page":"22436-22441","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":346,"title":["Inferring social ties from geographic coincidences"],"prefix":"10.1073","volume":"107","author":[{"given":"David J.","family":"Crandall","sequence":"first","affiliation":[{"name":"School of Informatics and Computing, Indiana University, Bloomington, IN 47403;"}]},{"given":"Lars","family":"Backstrom","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Cornell University, Ithaca, NY 14853; and"}]},{"given":"Dan","family":"Cosley","sequence":"additional","affiliation":[{"name":"Department of Information Science, Cornell University, Ithaca, NY 14853"}]},{"given":"Siddharth","family":"Suri","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Cornell University, Ithaca, NY 14853; and"}]},{"given":"Daniel","family":"Huttenlocher","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Cornell University, Ithaca, NY 14853; and"}]},{"given":"Jon","family":"Kleinberg","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Cornell University, Ithaca, NY 14853; and"}]}],"member":"341","published-online":{"date-parts":[[2010,12,8]]},"reference":[{"key":"e_1_3_3_1_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.167.3924.1461"},{"key":"e_1_3_3_2_2","doi-asserted-by":"publisher","DOI":"10.2307\/1597797"},{"key":"e_1_3_3_3_2","volume-title":"The New Politics of Surveillance and Visibility","author":"Haggerty KD","year":"2006","unstructured":", eds KD Haggerty, RV Ericson (University of Toronto Press, Toronto The New Politics of Surveillance and Visibility, 2006)."},{"key":"e_1_3_3_4_2","doi-asserted-by":"publisher","DOI":"10.1086\/427976"},{"key":"e_1_3_3_5_2","doi-asserted-by":"publisher","DOI":"10.1038\/nature04292"},{"key":"e_1_3_3_6_2","doi-asserted-by":"publisher","DOI":"10.1038\/nature06958"},{"key":"e_1_3_3_7_2","doi-asserted-by":"publisher","DOI":"10.1090\/conm\/001"},{"key":"e_1_3_3_8_2","volume-title":"Probabilistic Reasoning in Intelligent Systems: Networks of Plausible Inference","author":"Pearl J","year":"1988","unstructured":"J Pearl Probabilistic Reasoning in Intelligent Systems: Networks of Plausible Inference (Morgan Kaufmann, San Mateo, CA, 1988)."},{"key":"e_1_3_3_9_2","doi-asserted-by":"publisher","DOI":"10.1109\/34.969114"},{"key":"e_1_3_3_10_2","doi-asserted-by":"publisher","DOI":"10.1080\/01621459.1989.10478847"},{"key":"e_1_3_3_11_2","first-page":"370","volume-title":"Proceedings of the 23rd Annual Conference of the Cognitive Science Society","author":"Griffiths TL","year":"2001","unstructured":"TL Griffiths, JB Tenenbaum, Randomness and coincidences: Reconciling intuition and probability theory. 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(2006)."},{"key":"e_1_3_3_17_2","first-page":"111","volume-title":"Proceedings of the 29th IEEE Symposium on Security and Privacy","author":"Narayanan A","year":"2008","unstructured":"A Narayanan, V Shmatikov, Robust de-anonymization of large sparse datasets (How to break anonymity of the Netflix prize dataset). Proceedings of the 29th IEEE Symposium on Security and Privacy, pp. 111\u2013125 (2008)."},{"key":"e_1_3_3_18_2","volume-title":"Proceedings of the 16th International World Wide Web Conference","author":"Backstrom L","year":"2007","unstructured":"L Backstrom, C Dwork, J Kleinberg, Wherefore art thou R3579X? Anonymized social networks, hidden patterns, and structural steganography. 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Transactions on Data Privacy 3, 91\u2013121 (2010).","journal-title":"Transactions on Data Privacy"},{"key":"e_1_3_3_24_2","first-page":"15274","volume-title":"Proc Natl Acad Sci USA","volume":"106","author":"Eagle N","year":"2009","unstructured":"N Eagle, A Pentland, D Lazer, Inferring social network structure using mobile phone data. Proc Natl Acad Sci USA 106, 15274\u201315278 (2009)."},{"key":"e_1_3_3_25_2","doi-asserted-by":"publisher","DOI":"10.1145\/1149941.1149949"}],"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.1006155107","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,14]],"date-time":"2022-04-14T09:13:31Z","timestamp":1649927611000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.1006155107"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2010,12,8]]},"references-count":25,"journal-issue":{"issue":"52","published-print":{"date-parts":[[2010,12,28]]}},"alternative-id":["10.1073\/pnas.1006155107"],"URL":"https:\/\/doi.org\/10.1073\/pnas.1006155107","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[2010,12,8]]},"assertion":[{"value":"2010-12-08","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}