Nolan McCarty

Methodological Issues in Bridging Ideal Points in Disparate Institutions in a Data Sparse Environment

In earlier work, we created Congressional common space scores for multiple state legislatures using bridge actors who served in both institutions. Here, we employ simulations to explore the general issues involved in bridging institutions in data-sparse environments, where only a few bridge actors exist to allow inter-institutional comparisons. We find that only a few such bridges are necessary to improve ideal point estimates of rescaled legislative chambers.

Partisan Polarization in the United States: Diagnoses and Avenues for Reform

Over the several decades, observers of American politics have noted the sharp increase in partisanship and ideological polarization among members of Congress. While better ideological differentiation may provide voters clearer choices and increase accountability, the results of recent partisan and ideological battles have raised questions about the impact pf polarization on good governance.While much scholarly effort has gone into studying the root causes on congressional polarization, such research has been hampered by its sole reliance on the US House and Senate for data on legislative polarization. But new data on polarization of state legislatures provided by Shor and McCarty (2011) and updated with the generous support of the John and Laura Arnold Foundation expands our capacity to uncover the political, economic, and social factors that underlie our increasingly polarized system.In this report, we review the evidence concerning the polarization of the US Congress and supplement it with analyses based on the experience of polarization in the US states. We show that while there is variation in polarization across states, in aggregate the patterns are very similar to the national experience. Moreover, analyses of the causes of polarization at the national level are generally confirmed by the data on the states. The richer data from the sates, however, allows us to address new sets of questions which suggest some limited opportunities for reforms targeted at reducing polarization.

Unequal Incomes, Ideology and Gridlock: How Rising Inequality Increases Political Polarization

Income inequality and political polarization have both increased dramatically in the United States over the last several decades. A small but growing literature has suggested that these two phenomena may be related and mutually reinforcing: income inequality leads to political polarization, and the gridlock induced by polarization reduces the ability of politicians to alleviate rising inequality. Scholars, however, have not credibly identied the causal relationships. Using newly available data on polarization in state legislatures and state-level income inequality, we extend previous analyses to the US state level. Employing a relatively underutilized instrumental variables identication strategy allows us to obtain the rst credible causal estimates of the eect of inequality on polarization within states. We nd that income inequality has a large, positive and statistically signicant

Dynamic Games of Incomplete Information

• Recall: static games of incomplete information – The game/payoffs depend on the type of players. A player knows its own type but it does not know the types of the other players. – Transform a game of incomplete information AE game of imperfect information • Assign probabilities for the types of the players • Perceived as a move by nature • Represents the players apriori belief on the types of other players • What changes for the dynamic game? – Players have the chance of updating their beliefs based on the observed actions of the other players.

Games in the Normal Form

At twelve and a half minutes into the broadcast, Detectives Logan and Briscoe arrest two murder suspects. District Attorney Adam Schiff instructs Assistant D.A. Jack McCoy to make the following offer to each separately: If you confess and provide evidence of first-degree murder by your accomplice, you will receive a 1 year sentence on a weapons charge provided that your accomplice does not confess. If she does confess as well, you both will get 8 years for murder II. If you hold out and your accomplice turns states evidence, you will serve 25 to life for murder I. If she also holds out, you will serve 4 years for voluntary manslaughter. Assuming each suspect loses one unit of utility for each year in prison, Table 5.1 shows the payoffs of each subject given all of the possible outcomes. The rows represent the actions of suspect 1 whereas the columns represent the actions of suspect 2. Each pair of numbers represents the payoffs for suspect 1 and suspect 2 for each combination, respectively. The situation of the suspects is strategic because the outcome of any action by suspect 1 depends on the choices of suspect 2, and vice versa. What should the suspects do? Collectively, they prefer to hold out. If they both hold out, the total jail time is only eight years, far less than any other outcome. Unless, however, they reach a binding agreement, the individual incentives of the suspects undermine this outcome.