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An Axiomatic Study of Scoring Rule Markets Frongillo, Rafael Waggoner, Bo prediction markets information elicitation scoring rules Prediction markets are well-studied in the case where predictions are probabilities or expectations of future random variables. In 2008, Lambert, et al. proposed a generalization, which we call "scoring rule markets" (SRMs), in which traders predict the value of arbitrary statistics of the random variables, provided these statistics can be elicited by a scoring rule. Surprisingly, despite active recent work on prediction markets, there has not yet been any investigation into more general SRMs. To initiate such a study, we ask the following question: in what sense are SRMs "markets"? We classify SRMs according to several axioms that capture potentially desirable qualities of a market, such as the ability to freely exchange goods (contracts) for money. Not all SRMs satisfy our axioms: once a contract is purchased in any market for prediction the median of some variable, there will not necessarily be any way to sell that contract back, even in a very weak sense. Our main result is a characterization showing that slight generalizations of cost-function-based markets are the only markets to satisfy all of our axioms for finite-outcome random variables. Nonetheless, we find that several SRMs satisfy weaker versions of our axioms, including a novel share-based market mechanism for ratios of expected values. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Rafael Frongillo and Bo Waggoner 2018 Is Part Of LIPIcs, Volume 94, 9th Innovations in Theoretical Computer Science Conference (ITCS 2018) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.ITCS.2018.15 urn:nbn:de:0030-drops-83611 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2018.15 eng https://creativecommons.org/licenses/by/3.0/legalcode