The Cambridge series on the Political Economy of Institutions and Decisions is built around attempts to answer two central questions: How do institutions evolve in response to individual incentives, strategies, and choices, and how do institutions affect the performance of political and economic systems? The scope of the series is comparative and historical rather than international or specifically American, and the focus is positive rather than normative.

Laver and Shepsle's theoretically innovative book pushes the study of government formation a big step forward. Rather than concentrating on the equilibrium collective policy that emerges from the balance and distribution of party strengths in the parliament, they treat governments as collections of ministers with individual jurisdictions and policy as a bundle of individual party-preferred policies, depending on which party receives which portfolio. Jurisdiction is the key concept, in their view. It makes a party's promises credible to its electors, for it can carry them out (only) if it receives the relevant ministry. At the same time portfolio allocation monitors party behavior, for the party receiving a portfolio has no excuse for not carrying out its preferred policy.

Their portfolio-based model of government formation is based on constitutional features carefully documented in a massive 14-country study, published in the companion volume Cabinet Ministers and Parliamentary Government. The model bases its predictions on a sequence of proposals from an historically determined status quo. Bargaining takes place among rationally foresighted policy-motivated parties, each with an explicit veto over every cabinet in which it could participate, in a lattice of feasible governments. Laver and Shepsle's predicted importance for “strong” parties opens up significant possibilities for comparative empirical evaluations of theirs and other contending models.