We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Random graphs

Following the 2016 U.S. presidential election, many have expressed concern about the effects of false stories (“fake news”), circulated largely through social media. We discuss the economics of fake news and present new data on its consumption prior to the election. Drawing on web browsing data, archives of fact-checking websites, and results from a new online survey, we find: (i) social media was an important but not dominant source of election news, with 14 percent of Americans calling social media their “most important” source; (ii) of the known false news stories that appeared in the three months before the election, those favoring Trump were shared a total of 30 million times on Facebook, while those favoring Clinton were shared 8 million times; (iii) the average American adult saw on the order of one or perhaps several fake news stories in the months around the election, with just over half of those who recalled seeing them believing them; and (iv) people are much more likely to believe stories that favor their preferred candidate, especially if they have ideologically segregated social media networks.

/pdf/social-media-and-fake-news-in-the-2016-election-1m4ttkb5mo.pdf

Social Media and Fake News in the 2016 Election

Framework Convention on Climate Change

We develop a theory of prosocial behavior that combines heterogeneity in individual altruism and greed with concerns for social reputation or self-respect. Rewards or punishments (whether material or imagerelated) create doubt about the true motive for which good deeds are performed and this “overjustification effect” can induce a partial or even net crowding out of prosocial behavior by extrinsic incentives. We also identify the settings that are conducive to multiple social norms and more generally those that make individual actions complements or substitutes, which we show depends on whether stigma or honor is (endogenously) the dominant reputational concern. Finally, we analyze the socially optimal level of incentives and how monopolistic or competitive sponsors depart from it. Sponsor competition is shown to potentially reduce social welfare.

/pdf/incentives-and-prosocial-behavior-tzz3wh6cov.pdf

Incentives and Prosocial Behavior

We build a theory of prosocial behavior that combines heterogeneity in individual altruism and greed with concerns for social reputation or self-respect. The presence of rewards or punishments creates doubt as to the true motive for which good deeds are performed, and this "overjustification effect" can result in a net crowding out of prosocial behavior by extrinsic incentives. The model also allows us to identify settings that are conducive to multiple social norms of behavior, and those where disclosing one's generosity may backfire. Finally, we analyze the equilibrium contracts offered by sponsors, including the level and confidentiality or publicity of incentives. Sponsor competition may cause rewards to bid down rather than up, and can even reduce social welfare by requiring agents to engage in inefficient sacrifices.

/pdf/incentives-and-prosocial-behavior-1fmfrk0247.pdf

In previous work on cheap talk, uncertainty has almost always been modeled using a single-dimensional state variable. In this paper we prove that the dimensionality of the uncertain variable has an important qualitative impact on results and yields interesting insights into the "mechanics" of information transmission. Contrary to the unidimensional case, if there is more than one sender, full revelation of information in all states of nature is generically possible, even when the conflict of interest is arbitrarily large. What really matters in transmission of information is the local behavior of senders' indifference curves at the ideal point of the receiver, not the proximity of players' ideal point.

/pdf/multiple-referrals-and-multidimensional-cheap-talk-59srtejq1k.pdf

Multiple Referrals and Multidimensional Cheap Talk

Cheap talk games have been widely used to analyze situations in which a policy maker needs expert advice. In previous work, agent uncertainty has almost always been modeled using a single-dimensional state variable. In this paper we prove that the dimensionality of the uncertain variable has an important qualitative impact on results and yields interesting insights into the 'mechanics' of information transmission. Contrary to the unidimensional case, with more than one dimension full transmission of information in all states of nature is typically possible, provided a very simple and intuitive condition is satisfied. When utilities are quadratic and there are simultaneous reports, linear independence of senders' ideal points is a sufficient condition to guarantee full revelation; with sequential reports, linear independence and a simple condition on the gradients of senders' utilities at the receiver's ideal point are sufficient. In particular as an application of the theory we are able to explain an empirical puzzle related to informational theories of legislative organization. These theories predict that legislative committees (senders) should have strong alignment of preferences with the Floor; but this doesn't fit with empirical facts. We prove that what really matters in transmission of information is the local behavior of the utilities of the senders at the ideal point of the policy maker (receiver), not the distances between the ideal points of players. We interpret this as an argument in support of informational theories of legislative organizations.

This paper presents a dynamic political economy theory of public spending, taxation and debt. Policy choices are made by a legislature consisting of representatives elected by geographically-defined districts. The legislature can raise revenues via a distortionary income tax and by borrowing. These revenues can be used tofinance a national public good and district-specific transfers (interpreted as pork-barrel spending). The value of the public good is stochastic, reflecting shocks such as wars or natural disasters. In equilibrium, policy-making cycles between two distinct regimes: “business-as-usual” in which legislators bargain over the allocation of pork, and “responsible-policy-making” in which policies maximize the collective good. Transitions between the two regimes are brought about by shocks in the value of the public good. In the long run, equilibrium tax rates are too high and too volatile, public good provision is too low and debt levels are too high. In some environments, a balanced budget requirement can improve citizen welfare.

/pdf/a-dynamic-theory-of-public-spending-taxation-and-debt-1wlj1ig5at.pdf

A dynamic theory of public spending, taxation and debt

To study how a firm can capitalize on a long-term customer relationship, we characterize the optimal contract between a monopolist and a consumer whose preferences follow a Markov process. The optimal contract is nonstationary and has infinite memory, but is described by a simple state variable. Under general conditions, supply converges to the efficient level for any degree of persistence of the types and along any history, though convergence is history-dependent. In contrast, as with constant types, the optimal contract can be renegotiation-proof, even with highly persistent types. These properties provide insights into the optimal ownership structure of the production technology.

Long-Term Contracting with Markovian Consumers

This paper develops an infinite horizon model of public spending and taxation in which policy decisions are determined by legislative bargaining. The policy space incorporates both productive and distributive public spending and distortionary taxation. The productive spending is investing in a public good that benefits all citizens (e.g., national defense) and the distributive spending is district-specific transfers (e.g., pork-barrel spending). Investment in the public good creates a dynamic linkage across policymaking periods. The analysis explores the dynamics of legislative policy choices, focusing on the efficiency of the steady-state level of

/pdf/inefficiency-in-legislative-policymaking-a-dynamic-analysis-drqumh2b9d.pdf

Marco Battaglini

Papers

Multiple Referrals and Multidimensional Cheap Talk

Multiple Referrals and Multidimensional Cheap Talk

A dynamic theory of public spending, taxation and debt

Long-Term Contracting with Markovian Consumers

Inefficiency in Legislative Policymaking: A Dynamic Analysis