Sourav Bhattacharya

Preference Monotonicity and Information Aggregation in Elections

I analyse informational e¢ ciency of two-alternative elections where the utility of the voters depends on the realisation of an uncertain, binary state variable about which voters receive an independent, noisy signal. I show that large elections aggregate information e¢ ciently for any voting rule in the unique equilibrium if and only if the set of voters who favour an alternative in one state includes the set which favours the same alternative in the other state. I call this the preference monotonicity condition. If preference monotonicity fails, we have two groups of voters such that a change in state induces their rankings to change in opposite ways; and I term this phenomenon as preference reversal. Under preference reversal, for large classes of voting rules we have equilibria (

Compulsory versus Voluntary Voting: An Experimental Study

We report on an experiment comparing compulsory and voluntary voting institutions in a voting game with common preferences. Rational choice theory predicts sharp differences in voter behavior between these two institutions. If voting is compulsory, then voters may find it rational to vote insincerely, i.e., against their private information. If voting is voluntary so that abstention is allowed, then sincere voting in accordance with a voters private information is always rational while participation may become strategic. We find strong support for these theoretical predictions in our experimental data. Moreover, voters adapt their decisions to the voting institution in place in such a way as to make the group decision accuracy differences between the two voting institutions negligible. The latter finding may serve to rationalize the co-existence of compulsory and voluntary voting institutions in nature.

On the optimality of diverse expert panels in persuasion games

We consider a persuasion game between a decision-maker and a panel of biased experts. The decision-maker prefers to take an action in [0, 1] that matches the underlying state but relies on the experts to learn the state. Each expert has his `ideal` action or `agenda` and may conceal unfavorable information. If the decision- maker can select the panel members based on their agendas, what panel would she choose? While common intuition favors diverse panel (as experts would restrict each other`s ability to alter information), Bhattacharya and Mukherjee (2013) presents an example where a `homogeneous` panel (either all have agenda 0, or all have agenda 1) is more conducive to information revelation than a `diverse` panel (where one expert`s agenda is 0 the other`s is 1). We analyze the optimal diversity in expert panels and show that under mild conditions, a homogeneous panel is optimal when the experts observe the state independently of each other. But if the observability of the state is correlated across experts, diverse panel may be optimal. Hence, the diversity of agendas must be considered in conjunction with the diversity of information sources, and it is never optimal to seek diversity in both dimensions.

Voting with endogenous information acquisition: Experimental evidence

The Condorcet jury model with costless but informative signals about the true state of the world predicts that the efficiency of group decision-making increases unambiguously with the group size. However, if signal acquisition is made an endogenous and costly decision, then rational voters have disincentives to purchase information as the group size becomes larger. We investigate the extent to which human subjects recognize this trade-off between better information aggregation and greater incentives to free-ride in a laboratory experiment where we vary the group size, the cost of information acquisition and the precision of signals. We find that the theory predicts well in the case of precise signals. However, when signals are imprecise, free-riding incentives appear to be much weaker as there is a pronounced tendency for subjects to over-acquire information relative to equilibrium predictions. We rationalize the latter finding using a quantal response equilibrium that allows for risk aversion.

Conflict and Mobility: Resource Sharing Among Groups

We study a political competition between two groups, where the winner has the decision rights to allocate resources, like political parties deciding on sharing of patronage goods. What factors determine how resources are shared? We highlight an important force that affects distribution of resources, namely the ability to move between groups. In many contexts, group sizes are determined endogenously. For example, allocation of jobs based on party allegiance may influence individuals’ choices of switching party membership. We analyze how the ease of inter-group mobility affects resource allocation. One insight from existing literature is that the threat of conflict can also act as a constraint to how exploitative the elite can be. We investigate the combined effect of both factors. We show how inter-group mobility affects the possibility of conflict and in turn the extent of resource sharing? We find that sharing occurs in equilibrium. There are two reasons why the incumbent wants to shares resources with the opposition. First, if the incumbent retains too much surplus, it may attract switchers, which reduces the per capita share. Second, sharing resources increases the oppositions opportunity cost of engaging in conflict. There are thus two constraints on expropriation - the switching constraint and the conflict constraint. Optimal sharing is dictated by whether the constraint s bind. We also find a non-monotonic relationship between resource sharing and the cost of mobility. Our predictions are consistent with several stylized facts that cannot be explained by earlier models.