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Abstract:
Ordinally single-peaked preferences are distinguished from cardinally single-peaked preferences, in which all players have a similar perception of distances in some one-dimensional ordering. While ordinal single-peakedness can lead to disconnected coalitions that have a "hole" in the ordering, cardinal single-peakedness precludes this possibility, based on two models of coalition formation:

- Fallback (FB): Players seek coalition partners by descending lower and lower in their preference rankings until a majority coalition forms.

- Build-Up (BU): Similar to FB, except that when nonmajority subcoalitions form, they fuse into composite players, whose positions are defined cardinally and who are treated as single players in the convergence process.

FB better reflects the unconstrained, or nonmyopic, possibilities of coalition formation, whereas BU - because all subcoalition members must be included in any majority coalition that forms - restricts combinatorial possibilities and tends to produce less compact majority coalitions. Applications of the models to legislatures, parliamentary coalitions, and military alliances are discussed.

Coalition formation, dynamic analysis, single-peakedness, legislatures

Abstract:
Players are assumed to rank each other as coalition partners.

Two processes of coalition formation are defined and illustrated:

- Fallback (FB): Players seek coalition partners by descending lower and lower in their preference rankings until some majority coalition, all of whose members consider each other mutually acceptable, forms.

- Build-up (BU): Same descent as FB, except only majorities whose members rank each other highest form coalitions.

BU coalitions are stable in the sense that no member would prefer to be in another coalition, whereas FB coalitions, whose members need not rank each other highest, may not be stable. BU coalitions are bimodally distributed in a random society, with peaks around simple majority and unanimity the distributions of majorities in the US Supreme Count and in the US House of Representatives follow this pattern. The dynamics of real-life coalition-formation processes are illustrated by two Supreme Court cases.

Coalition dynamics, Fallback bargaining, Manipulability, Legislatures, US Supreme Court

Abstract:
Increasingly skeptical about the efficiency and effectiveness of formal multilateral enforcement mechanisms, a growing number of international relations theorists and international lawyers have begun to argue that states' reputational concerns are actually the principal mechanism for maintaining a high level of treaty compliance. This essay argues that there are a number of empirical and theoretical reasons for believing that the actual effects of reputation are both weaker and more complicated than the standard view of reputation suggests. While states have reason to revise their estimates of a state's reputation following a defection or pattern of defections, they have reason to do so only in connection with those agreements that they believe are (1) affected by the same or similar sources of fluctuating compliance costs and (2) believed to be valued the same or less by the defecting state. This tends to localize the consequences of noncompliance on reputation to a subset of similar agreements.