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Gibbard's theorem

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If there are only 2 possible outcomes, a game form may be strategyproof and not dictatorial. For example, it is the case of the simple majority vote: each voter casts a ballot for her most-liked alternative (among the two possible outcomes), and the alternative with most votes is declared the winner.
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is defined as follows. If voter 1 has a unique most-liked candidate, then this candidate is elected. Otherwise, possible outcomes are restricted to his ex-aequo most-liked candidates and the other candidates are eliminated. Then voter 2's ballot is examined: if he has a unique best-liked candidate
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This game form is strategyproof because it is always optimal to vote for one's most-liked alternative (unless one is indifferent between them). However, it is clearly not dictatorial. Many other game forms are strategyproof and not dictatorial: for example, assume that the alternative
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The terminology for this varies. Gibbard states that 'an individual "manipulates" the voting scheme if, by misrepresenting his preferences, he secures an outcome he prefers to the "honest" outcome', while Brams and Fishburn call every ballot with an honest ordering
2281:. This game form is clearly dictatorial, because voter 1 can impose the result. However, it is not strategyproof: the other voters face the same issue of strategic voting as in the usual Borda count. Thus, Gibbard's theorem is an implication and not an equivalence. 2175:
among the non-eliminated ones, then this candidate is elected. Otherwise, the list of possible outcomes is reduced again, etc. If there is still several non-eliminated candidates after all ballots have been examined, then an arbitrary tie-breaking rule is used.
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Gibbard's theorem states that a deterministic process of collective decision cannot be strategyproof, except possibly in two cases: if there is a distinguished agent who has a dictatorial power, or if the process limits the outcome to two possible options only.
987:: once the voter has identified her own preferences, she does not have a ballot at her disposal that best defends her opinions in all situations; she needs to act strategically, possibly by spying over the other voters to determine how they intend to vote. 2276:
Consider the following game form. Voter 1 can vote for a candidate of her choice, or she can abstain. In the first case, the specified candidate is automatically elected. Otherwise, the other voters use a classic voting rule, for example the
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This game form is strategyproof: whatever the preferences of a voter, he has a dominant strategy that consists in declaring his sincere preference order. It is also dictatorial, and its dictator is voter 1: if he wishes to see candidate
1808: 367:. Once the ballots are collected, the candidate with highest total grade is declared the winner. Ties between candidates are broken by alphabetical order: for example, if there is a tie between candidates 104:. Because of its broader scope, Gibbard's theorem makes no claim about whether voters need to reverse their ranking of candidates, only that their optimal ballots depend on the other voters' ballots. 107:
Gibbard's theorem is more general, and considers processes of collective decision that may not be ordinal: for example, voting systems where voters assign grades to or otherwise rate candidates (
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in 1973. It states that for any deterministic process of collective decision, at least one of the following three properties must hold:
2471: 97: 38: 2466: 112: 2517: 134: 2507: 1034: 1360:, but with no utilities associated to the possible outcomes: it describes the procedure only, without specifying 119: 100:
about voting rules. The key difference between the two theorems is that Gibbard–Satterthwaite applies only to
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that best defends her preferences, with no need to know or guess the strategies chosen by the other agents.
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If a game form is not dictatorial and has at least 3 possible outcomes, then it is not strategyproof.
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Gibbard's theorem assumes the collective decision results in exactly one winner and does not apply to
269:: each voter assigns to each candidate the grade 1 (approval) or 0 (withhold approval). For example, 123: 63: 2401: 1956: 1002: 33: 2451:
Strategy proofness of voting procedures with lotteries as outcomes and infinite sets of strategies
1322:{\displaystyle (s_{1},\ldots ,s_{n})\in {\mathcal {S}}_{1}\times \cdots \times {\mathcal {S}}_{n}} 510:. Which ballot will best defend her opinions? For example, consider the two following situations. 2432: 2382: 2339: 130: 2374: 1648:). This property is desirable for a democratic decision process: it means that once the agent 1388: 948: 910: 828: 770: 712: 674: 633: 555: 517: 272: 2424: 2416: 2366: 2331: 907:
faces a strategic voting dilemma: depending on the ballots that the other voters will cast,
89: 59: 1671: 1624: 1549: 1522: 1423: 266: 108: 1803:{\displaystyle {\mathcal {S}}={\mathcal {S}}_{1}\times \cdots \times {\mathcal {S}}_{n}} 983:
can be a ballot that best defends her opinions. We then say that approval voting is not
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However, if we assume instead that the two other voters respectively cast ballots
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The process is not straightforward; the optimal ballot for a voter "requires
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has only one ballot that leads to the election of her favorite alternative
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is an authorized ballot: it means that the voter approves of candidates
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has at least 3 possible outcomes if and only if the cardinality of
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elected, then he just has to communicate a preference order where
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Brams, Steven J.; Fishburn, Peter C. (1978). "Approval Voting".
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has a strategy at her disposal that ensures that the result is
2402:"Straightforwardness of Game Forms with Lotteries as Outcomes" 82:, i.e. there is a single voter whose vote chooses the outcome. 18: 1977:
is not assumed to be finite, the subset of possible outcomes
1353:. In other words, a game form is essentially defined like an 85:
The process limits the possible outcomes to two options only.
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depending on the context of application. For each agent
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who wish to select an option among three alternatives:
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is finite also; thus, even if the set of alternatives
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the gain that each agent would get from each outcome.
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A game form showing that the converse does not hold
2317:"Manipulation of voting schemes: A general result" 2260: 2240: 2211: 2191: 2134: 2114: 2094: 2051: 2025: 2002: 1969: 1945: 1920:is 3 or more. Since the strategy sets are finite, 1912: 1879: 1855: 1835: 1802: 1735: 1687: 1660: 1640: 1613: 1565: 1538: 1511: 1487: 1439: 1409: 1379: 1341: 1321: 1229: 1209: 1189: 1158: 1134: 1103: 1071: 1015: 975: 937: 899: 875: 855: 817: 797: 759: 739: 701: 660: 622: 602: 582: 544: 514:If the two other voters respectively cast ballots 502: 482: 462: 442: 419: 399: 379: 359: 339: 319: 299: 257: 237: 217: 197: 177: 157: 133:. A similar result for multi-winner voting is the 1447:over the alternatives, there exists a strategy 1072:{\displaystyle {\mathcal {N}}=\{1,\ldots ,n\}} 2248:wins if it gets two thirds of the votes, and 2063:, in the sense that for any possible outcome 8: 1066: 1048: 2146: 1867:of the game form. For example, we say that 118:Gibbard's theorem is itself generalized by 32:It has been suggested that this article be 16:Impossibility of straightforward game forms 2253: 2233: 2204: 2184: 2166:We assume that each voter communicates a 2127: 2107: 2083: 2082: 2068: 2044: 2018: 1991: 1990: 1982: 1961: 1960: 1958: 1934: 1933: 1925: 1901: 1900: 1892: 1872: 1848: 1824: 1823: 1815: 1794: 1788: 1787: 1771: 1765: 1764: 1754: 1753: 1751: 1724: 1711: 1706: 1700: 1679: 1673: 1653: 1632: 1626: 1602: 1589: 1584: 1578: 1557: 1551: 1530: 1524: 1504: 1476: 1463: 1458: 1452: 1431: 1425: 1402: 1372: 1334: 1313: 1307: 1306: 1290: 1284: 1283: 1270: 1251: 1242: 1222: 1202: 1181: 1175: 1174: 1171: 1151: 1126: 1120: 1119: 1116: 1096: 1039: 1038: 1036: 1007: 1006: 1004: 950: 912: 892: 868: 830: 810: 772: 752: 714: 676: 635: 615: 595: 557: 519: 495: 475: 455: 435: 412: 392: 372: 352: 332: 312: 274: 250: 230: 210: 190: 170: 150: 111:). Gibbard's theorem can be proven using 2304: 2289: 1142:be a set that represents the available 2095:{\displaystyle a\in g({\mathcal {S}})} 7: 2219:is the unique most-liked candidate. 1329:, maps an alternative. The function 1668:has identified her own preferences 96:A corollary of this theorem is the 1190:{\displaystyle {\mathcal {S}}_{i}} 1135:{\displaystyle {\mathcal {S}}_{i}} 347:but does not approve of candidate 70:is a result proven by philosopher 14: 2359:American Political Science Review 2003:{\displaystyle g({\mathcal {S}})} 1946:{\displaystyle g({\mathcal {S}})} 1913:{\displaystyle g({\mathcal {S}})} 1836:{\displaystyle g({\mathcal {S}})} 2513:Theorems in discrete mathematics 2479: 1736:{\displaystyle s_{i}^{*}(P_{i})} 1614:{\displaystyle s_{i}^{*}(P_{i})} 1488:{\displaystyle s_{i}^{*}(P_{i})} 23: 2089: 2079: 1997: 1987: 1970:{\displaystyle {\mathcal {A}}} 1940: 1930: 1907: 1897: 1830: 1820: 1730: 1717: 1608: 1595: 1482: 1469: 1276: 1244: 1016:{\displaystyle {\mathcal {A}}} 970: 952: 932: 914: 850: 832: 792: 774: 734: 716: 696: 678: 655: 637: 577: 559: 539: 521: 294: 276: 1: 2472:Gibbard–Satterthwaite theorem 2467:Arrow's impossibility theorem 113:Arrow's impossibility theorem 98:Gibbard–Satterthwaite theorem 49:Proposed since November 2023. 39:Gibbard–Satterthwaite theorem 1695:, she can choose a strategy 1217:be a function that, to each 1031:in a context of voting. Let 825:win; she should rather vote 1083:, which can also be called 1027:, which can also be called 2534: 2170:over the candidates. The 2039:if there exists an agent 1519:when she has preferences 2400:Gibbard, Allan (1978). 976:{\displaystyle (1,1,0)} 938:{\displaystyle (1,0,0)} 856:{\displaystyle (1,1,0)} 798:{\displaystyle (1,0,0)} 740:{\displaystyle (0,1,1)} 702:{\displaystyle (0,0,1)} 661:{\displaystyle (1,0,0)} 583:{\displaystyle (1,1,1)} 545:{\displaystyle (0,1,1)} 300:{\displaystyle (1,1,0)} 135:Duggan–Schwartz theorem 2262: 2242: 2213: 2193: 2136: 2116: 2096: 2053: 2027: 2004: 1971: 1947: 1914: 1881: 1863:, i.e. the set of the 1857: 1837: 1804: 1737: 1689: 1662: 1642: 1615: 1567: 1540: 1513: 1489: 1441: 1411: 1381: 1343: 1323: 1231: 1211: 1191: 1160: 1136: 1105: 1073: 1017: 977: 939: 901: 877: 857: 819: 799: 761: 741: 703: 662: 624: 604: 584: 546: 504: 484: 464: 444: 421: 401: 381: 361: 341: 321: 301: 259: 239: 219: 199: 179: 159: 120:Gibbard's 1978 theorem 2263: 2243: 2214: 2194: 2137: 2117: 2097: 2054: 2028: 2005: 1972: 1948: 1915: 1882: 1858: 1838: 1805: 1738: 1690: 1688:{\displaystyle P_{i}} 1663: 1643: 1641:{\displaystyle P_{i}} 1616: 1568: 1566:{\displaystyle s_{i}} 1541: 1539:{\displaystyle P_{i}} 1514: 1490: 1442: 1440:{\displaystyle P_{i}} 1412: 1382: 1344: 1324: 1237:-tuple of strategies 1232: 1212: 1192: 1161: 1137: 1106: 1074: 1018: 978: 940: 902: 878: 858: 820: 800: 762: 742: 704: 663: 625: 605: 585: 547: 505: 485: 465: 445: 422: 402: 382: 362: 342: 322: 302: 260: 240: 220: 200: 180: 160: 145:Consider some voters 2518:Social choice theory 2285:Notes and references 2252: 2232: 2223:Simple majority vote 2203: 2183: 2126: 2106: 2067: 2043: 2017: 1981: 1957: 1924: 1891: 1871: 1847: 1814: 1750: 1699: 1672: 1652: 1625: 1577: 1550: 1523: 1503: 1451: 1424: 1401: 1393:(originally called: 1371: 1333: 1241: 1221: 1201: 1170: 1150: 1115: 1095: 1035: 1003: 949: 911: 891: 867: 829: 809: 771: 751: 713: 675: 634: 614: 594: 556: 518: 494: 474: 454: 450:prefers alternative 434: 411: 391: 371: 351: 331: 311: 273: 249: 229: 209: 189: 169: 149: 64:social choice theory 2172:serial dictatorship 2162:Serial dictatorship 2150: —  2010:is necessarily so. 1716: 1594: 1468: 1397:) if for any agent 131:multi-winner voting 2508:Economics theorems 2258: 2238: 2209: 2189: 2148: 2132: 2112: 2092: 2049: 2023: 2000: 1967: 1943: 1910: 1877: 1853: 1833: 1800: 1733: 1702: 1685: 1658: 1638: 1611: 1580: 1563: 1536: 1509: 1485: 1454: 1437: 1407: 1377: 1339: 1319: 1227: 1207: 1187: 1156: 1132: 1101: 1069: 1013: 973: 935: 897: 873: 853: 815: 795: 757: 737: 699: 658: 620: 600: 580: 542: 500: 480: 460: 440: 430:Assume that voter 417: 397: 377: 357: 337: 317: 297: 265:. Assume they use 255: 235: 215: 195: 175: 155: 2449:Hylland, Aanund. 2261:{\displaystyle b} 2241:{\displaystyle a} 2212:{\displaystyle a} 2192:{\displaystyle a} 2168:strict weak order 2147:Gibbard's theorem 2135:{\displaystyle a} 2115:{\displaystyle i} 2052:{\displaystyle i} 2026:{\displaystyle g} 1880:{\displaystyle g} 1865:possible outcomes 1856:{\displaystyle g} 1661:{\displaystyle i} 1573:, different from 1512:{\displaystyle i} 1419:strict weak order 1410:{\displaystyle i} 1380:{\displaystyle g} 1342:{\displaystyle g} 1230:{\displaystyle n} 1210:{\displaystyle g} 1159:{\displaystyle i} 1104:{\displaystyle i} 900:{\displaystyle 1} 887:To sum up, voter 876:{\displaystyle b} 818:{\displaystyle c} 805:because it makes 760:{\displaystyle 1} 623:{\displaystyle a} 603:{\displaystyle 1} 503:{\displaystyle c} 483:{\displaystyle b} 463:{\displaystyle a} 443:{\displaystyle 1} 420:{\displaystyle a} 400:{\displaystyle b} 380:{\displaystyle a} 360:{\displaystyle c} 340:{\displaystyle b} 320:{\displaystyle a} 258:{\displaystyle c} 238:{\displaystyle b} 218:{\displaystyle a} 198:{\displaystyle 3} 178:{\displaystyle 2} 158:{\displaystyle 1} 124:Hylland's theorem 68:Gibbard's theorem 58:In the fields of 56: 55: 51: 2525: 2489: 2484: 2483: 2454: 2447: 2441: 2440: 2406: 2397: 2391: 2390: 2354: 2348: 2347: 2321: 2309: 2298: 2294: 2268:wins otherwise. 2267: 2265: 2264: 2259: 2247: 2245: 2244: 2239: 2218: 2216: 2215: 2210: 2198: 2196: 2195: 2190: 2151: 2141: 2139: 2138: 2133: 2121: 2119: 2118: 2113: 2101: 2099: 2098: 2093: 2088: 2087: 2058: 2056: 2055: 2050: 2032: 2030: 2029: 2024: 2009: 2007: 2006: 2001: 1996: 1995: 1976: 1974: 1973: 1968: 1966: 1965: 1952: 1950: 1949: 1944: 1939: 1938: 1919: 1917: 1916: 1911: 1906: 1905: 1886: 1884: 1883: 1878: 1862: 1860: 1859: 1854: 1842: 1840: 1839: 1834: 1829: 1828: 1809: 1807: 1806: 1801: 1799: 1798: 1793: 1792: 1776: 1775: 1770: 1769: 1759: 1758: 1742: 1740: 1739: 1734: 1729: 1728: 1715: 1710: 1694: 1692: 1691: 1686: 1684: 1683: 1667: 1665: 1664: 1659: 1647: 1645: 1644: 1639: 1637: 1636: 1620: 1618: 1617: 1612: 1607: 1606: 1593: 1588: 1572: 1570: 1569: 1564: 1562: 1561: 1545: 1543: 1542: 1537: 1535: 1534: 1518: 1516: 1515: 1510: 1494: 1492: 1491: 1486: 1481: 1480: 1467: 1462: 1446: 1444: 1443: 1438: 1436: 1435: 1416: 1414: 1413: 1408: 1386: 1384: 1383: 1378: 1348: 1346: 1345: 1340: 1328: 1326: 1325: 1320: 1318: 1317: 1312: 1311: 1295: 1294: 1289: 1288: 1275: 1274: 1256: 1255: 1236: 1234: 1233: 1228: 1216: 1214: 1213: 1208: 1196: 1194: 1193: 1188: 1186: 1185: 1180: 1179: 1165: 1163: 1162: 1157: 1141: 1139: 1138: 1133: 1131: 1130: 1125: 1124: 1110: 1108: 1107: 1102: 1078: 1076: 1075: 1070: 1044: 1043: 1022: 1020: 1019: 1014: 1012: 1011: 995:Formal statement 982: 980: 979: 974: 944: 942: 941: 936: 906: 904: 903: 898: 882: 880: 879: 874: 862: 860: 859: 854: 824: 822: 821: 816: 804: 802: 801: 796: 767:should not vote 766: 764: 763: 758: 746: 744: 743: 738: 708: 706: 705: 700: 667: 665: 664: 659: 629: 627: 626: 621: 609: 607: 606: 601: 589: 587: 586: 581: 551: 549: 548: 543: 509: 507: 506: 501: 489: 487: 486: 481: 469: 467: 466: 461: 449: 447: 446: 441: 426: 424: 423: 418: 406: 404: 403: 398: 386: 384: 383: 378: 366: 364: 363: 358: 346: 344: 343: 338: 326: 324: 323: 318: 306: 304: 303: 298: 264: 262: 261: 256: 244: 242: 241: 236: 224: 222: 221: 216: 204: 202: 201: 196: 184: 182: 181: 176: 164: 162: 161: 156: 90:strategic voting 60:mechanism design 47: 27: 26: 19: 2533: 2532: 2528: 2527: 2526: 2524: 2523: 2522: 2493: 2492: 2485: 2478: 2463: 2458: 2457: 2448: 2444: 2421:10.2307/1914235 2404: 2399: 2398: 2394: 2371:10.2307/1955105 2356: 2355: 2351: 2336:10.2307/1914083 2319: 2311: 2310: 2306: 2301: 2295: 2291: 2287: 2274: 2250: 2249: 2230: 2229: 2225: 2201: 2200: 2181: 2180: 2164: 2159: 2154: 2149: 2124: 2123: 2104: 2103: 2065: 2064: 2041: 2040: 2015: 2014: 1979: 1978: 1955: 1954: 1922: 1921: 1889: 1888: 1869: 1868: 1845: 1844: 1812: 1811: 1786: 1763: 1748: 1747: 1720: 1697: 1696: 1675: 1670: 1669: 1650: 1649: 1628: 1623: 1622: 1598: 1575: 1574: 1553: 1548: 1547: 1526: 1521: 1520: 1501: 1500: 1472: 1449: 1448: 1427: 1422: 1421: 1399: 1398: 1395:straightforward 1369: 1368: 1331: 1330: 1305: 1282: 1266: 1247: 1239: 1238: 1219: 1218: 1199: 1198: 1197:is finite. Let 1173: 1168: 1167: 1148: 1147: 1118: 1113: 1112: 1093: 1092: 1033: 1032: 1001: 1000: 997: 947: 946: 909: 908: 889: 888: 865: 864: 827: 826: 807: 806: 769: 768: 749: 748: 711: 710: 673: 672: 632: 631: 612: 611: 592: 591: 554: 553: 516: 515: 492: 491: 472: 471: 452: 451: 432: 431: 409: 408: 389: 388: 369: 368: 349: 348: 329: 328: 309: 308: 271: 270: 267:approval voting 247: 246: 227: 226: 207: 206: 187: 186: 167: 166: 147: 146: 143: 109:cardinal voting 78:The process is 52: 28: 24: 17: 12: 11: 5: 2531: 2529: 2521: 2520: 2515: 2510: 2505: 2495: 2494: 2491: 2490: 2487:Economy portal 2475: 2474: 2469: 2462: 2459: 2456: 2455: 2442: 2415:(3): 595–614. 2392: 2365:(3): 831–847. 2349: 2330:(4): 587–601. 2313:Gibbard, Allan 2303: 2302: 2300: 2299: 2288: 2286: 2283: 2273: 2270: 2257: 2237: 2224: 2221: 2208: 2188: 2163: 2160: 2158: 2155: 2144: 2131: 2111: 2091: 2086: 2081: 2078: 2075: 2072: 2048: 2022: 1999: 1994: 1989: 1986: 1964: 1942: 1937: 1932: 1929: 1909: 1904: 1899: 1896: 1876: 1852: 1832: 1827: 1822: 1819: 1810:and denote by 1797: 1791: 1785: 1782: 1779: 1774: 1768: 1762: 1757: 1732: 1727: 1723: 1719: 1714: 1709: 1705: 1682: 1678: 1657: 1635: 1631: 1610: 1605: 1601: 1597: 1592: 1587: 1583: 1560: 1556: 1533: 1529: 1508: 1484: 1479: 1475: 1471: 1466: 1461: 1457: 1434: 1430: 1406: 1376: 1338: 1316: 1310: 1304: 1301: 1298: 1293: 1287: 1281: 1278: 1273: 1269: 1265: 1262: 1259: 1254: 1250: 1246: 1226: 1206: 1184: 1178: 1166:; assume that 1155: 1129: 1123: 1100: 1079:be the set of 1068: 1065: 1062: 1059: 1056: 1053: 1050: 1047: 1042: 1023:be the set of 1010: 996: 993: 972: 969: 966: 963: 960: 957: 954: 934: 931: 928: 925: 922: 919: 916: 896: 885: 884: 872: 863:, which makes 852: 849: 846: 843: 840: 837: 834: 814: 794: 791: 788: 785: 782: 779: 776: 756: 736: 733: 730: 727: 724: 721: 718: 698: 695: 692: 689: 686: 683: 680: 669: 657: 654: 651: 648: 645: 642: 639: 619: 599: 579: 576: 573: 570: 567: 564: 561: 541: 538: 535: 532: 529: 526: 523: 499: 479: 459: 439: 416: 396: 376: 356: 336: 316: 296: 293: 290: 287: 284: 281: 278: 254: 234: 214: 194: 174: 154: 142: 139: 94: 93: 86: 83: 54: 53: 31: 29: 22: 15: 13: 10: 9: 6: 4: 3: 2: 2530: 2519: 2516: 2514: 2511: 2509: 2506: 2504: 2503:Voting theory 2501: 2500: 2498: 2488: 2482: 2477: 2473: 2470: 2468: 2465: 2464: 2460: 2452: 2446: 2443: 2438: 2434: 2430: 2426: 2422: 2418: 2414: 2410: 2403: 2396: 2393: 2388: 2384: 2380: 2376: 2372: 2368: 2364: 2360: 2353: 2350: 2345: 2341: 2337: 2333: 2329: 2325: 2318: 2314: 2308: 2305: 2293: 2290: 2284: 2282: 2280: 2271: 2269: 2255: 2235: 2222: 2220: 2206: 2186: 2176: 2173: 2169: 2161: 2156: 2153: 2143: 2129: 2109: 2076: 2073: 2070: 2062: 2046: 2038: 2037: 2020: 2011: 1984: 1927: 1894: 1874: 1866: 1850: 1843:the range of 1817: 1795: 1783: 1780: 1777: 1772: 1760: 1744: 1725: 1721: 1712: 1707: 1703: 1680: 1676: 1655: 1633: 1629: 1603: 1599: 1590: 1585: 1581: 1558: 1554: 1531: 1527: 1506: 1498: 1477: 1473: 1464: 1459: 1455: 1432: 1428: 1420: 1404: 1396: 1392: 1391: 1390:strategyproof 1374: 1365: 1363: 1359: 1357: 1352: 1336: 1314: 1302: 1299: 1296: 1291: 1279: 1271: 1267: 1263: 1260: 1257: 1252: 1248: 1224: 1204: 1182: 1153: 1145: 1127: 1098: 1090: 1086: 1082: 1063: 1060: 1057: 1054: 1051: 1045: 1030: 1026: 994: 992: 988: 986: 985:strategyproof 967: 964: 961: 958: 955: 929: 926: 923: 920: 917: 894: 870: 847: 844: 841: 838: 835: 812: 789: 786: 783: 780: 777: 754: 747:, then voter 731: 728: 725: 722: 719: 693: 690: 687: 684: 681: 670: 652: 649: 646: 643: 640: 617: 597: 590:, then voter 574: 571: 568: 565: 562: 536: 533: 530: 527: 524: 513: 512: 511: 497: 477: 457: 437: 428: 414: 394: 374: 354: 334: 314: 291: 288: 285: 282: 279: 268: 252: 232: 212: 192: 172: 152: 140: 138: 136: 132: 127: 125: 121: 116: 114: 110: 105: 103: 102:ranked voting 99: 91: 87: 84: 81: 77: 76: 75: 73: 72:Allan Gibbard 69: 65: 61: 50: 45: 41: 40: 35: 30: 21: 20: 2445: 2429:10419/220562 2412: 2409:Econometrica 2408: 2395: 2362: 2358: 2352: 2327: 2324:Econometrica 2323: 2307: 2292: 2275: 2226: 2177: 2171: 2165: 2145: 2060: 2034: 2013:We say that 2012: 1864: 1745: 1496: 1417:and for any 1394: 1389: 1367:We say that 1366: 1361: 1358:-player game 1355: 1350: 1349:is called a 1143: 1088: 1084: 1080: 1028: 1025:alternatives 1024: 998: 989: 886: 429: 144: 128: 117: 106: 95: 67: 57: 48: 37: 2279:Borda count 2036:dictatorial 80:dictatorial 2497:Categories 2297:"sincere." 1499:for agent 1146:for agent 1144:strategies 1029:candidates 2379:0003-0554 2074:∈ 2059:who is a 1784:× 1781:⋯ 1778:× 1713:∗ 1591:∗ 1465:∗ 1351:game form 1303:× 1300:⋯ 1297:× 1280:∈ 1261:… 1058:… 490:and then 2461:See also 2315:(1973). 2157:Examples 2102:, agent 2061:dictator 1497:dominant 1495:that is 1362:a priori 630: : 141:Overview 2453:, 1980. 2437:1914235 2387:1955105 2344:1914083 1746:We let 1089:voters, 1085:players 470:, then 407:, then 44:Discuss 2435:  2385:  2377:  2342:  1111:, let 1081:agents 427:wins. 34:merged 2433:JSTOR 2405:(PDF) 2383:JSTOR 2340:JSTOR 2320:(PDF) 36:into 2375:ISSN 999:Let 883:win. 709:and 552:and 387:and 327:and 245:and 185:and 122:and 62:and 2425:hdl 2417:doi 2367:doi 2332:doi 2033:is 1387:is 1087:or 945:or 42:. ( 2499:: 2431:. 2423:. 2413:46 2411:. 2407:. 2381:. 2373:. 2363:72 2361:. 2338:. 2328:41 2326:. 2322:. 225:, 165:, 137:. 115:. 66:, 2439:. 2427:: 2419:: 2389:. 2369:: 2346:. 2334:: 2256:b 2236:a 2207:a 2187:a 2130:a 2110:i 2090:) 2085:S 2080:( 2077:g 2071:a 2047:i 2021:g 1998:) 1993:S 1988:( 1985:g 1963:A 1941:) 1936:S 1931:( 1928:g 1908:) 1903:S 1898:( 1895:g 1875:g 1851:g 1831:) 1826:S 1821:( 1818:g 1796:n 1790:S 1773:1 1767:S 1761:= 1756:S 1731:) 1726:i 1722:P 1718:( 1708:i 1704:s 1681:i 1677:P 1656:i 1634:i 1630:P 1609:) 1604:i 1600:P 1596:( 1586:i 1582:s 1559:i 1555:s 1532:i 1528:P 1507:i 1483:) 1478:i 1474:P 1470:( 1460:i 1456:s 1433:i 1429:P 1405:i 1375:g 1356:n 1337:g 1315:n 1309:S 1292:1 1286:S 1277:) 1272:n 1268:s 1264:, 1258:, 1253:1 1249:s 1245:( 1225:n 1205:g 1183:i 1177:S 1154:i 1128:i 1122:S 1099:i 1067:} 1064:n 1061:, 1055:, 1052:1 1049:{ 1046:= 1041:N 1009:A 971:) 968:0 965:, 962:1 959:, 956:1 953:( 933:) 930:0 927:, 924:0 921:, 918:1 915:( 895:1 871:b 851:) 848:0 845:, 842:1 839:, 836:1 833:( 813:c 793:) 790:0 787:, 784:0 781:, 778:1 775:( 755:1 735:) 732:1 729:, 726:1 723:, 720:0 717:( 697:) 694:1 691:, 688:0 685:, 682:0 679:( 668:. 656:) 653:0 650:, 647:0 644:, 641:1 638:( 618:a 598:1 578:) 575:1 572:, 569:1 566:, 563:1 560:( 540:) 537:1 534:, 531:1 528:, 525:0 522:( 498:c 478:b 458:a 438:1 415:a 395:b 375:a 355:c 335:b 315:a 295:) 292:0 289:, 286:1 283:, 280:1 277:( 253:c 233:b 213:a 193:3 173:2 153:1 46:)

Index

merged
Gibbard–Satterthwaite theorem
Discuss
mechanism design
social choice theory
Allan Gibbard
dictatorial
strategic voting
Gibbard–Satterthwaite theorem
ranked voting
cardinal voting
Arrow's impossibility theorem
Gibbard's 1978 theorem
Hylland's theorem
multi-winner voting
Duggan–Schwartz theorem
approval voting
strategyproof
n-player game
strategyproof
strict weak order
dictatorial
strict weak order
Borda count
Gibbard, Allan
"Manipulation of voting schemes: A general result"
doi
10.2307/1914083
JSTOR
1914083

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