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We study cooperation in economies of indefinite duration. Participants faced a sequence of prisoner’s dilemmas with anonymous opponents. We identify and characterize the strategies employed at the individual level. We report that (i) grim trigger does not describe well individual play and there is wide heterogeneity in strategies; (ii) systematic defection does not crowd-out systematic cooperation; (iii) coordination on cooperative strategies does not improve with experience. We discuss alternative methodologies and implications for theory.


NOTICE: this is the author’s version of a work that was accepted for publication in Games and Economic Behavior. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Games and Economic Behavior, volume 75 (2012). DOI: 10.1016/j.geb.2012.02.009

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