I develop a model of (individually rational) collective reality denial in groups, organizations and markets. Whether participants' tendencies toward wishful thinking reinforce or dampen each other is shown to hinge on a simple and novel mechanism. When an agent can expect to benefit from other's...

We find large effects on the earnings of participants from a randomized intervention that gave psychosocial stimulation to stunted Jamaican toddlers living in poverty. The intervention consisted of one-hour weekly visits from community Jamaican health workers over a 2-year period that taught...

This paper is a non-technical and somewhat philosophical essay, that seeks to investigate the relationship between economics and reality. More precisely, it asks how reality in the form empirical evidence does or does not influence economic thinking and theory. In particular, which role do...

This chapter provides a selective review of some contemporary approaches to program evaluation. One motivation for our review is the recent emergence and increasing use of a particular kind of "program" in applied microeconomic research, the so-called Regression Discontinuity (RD) Design of...

We develop a Roy model of social interactions in which individuals sort into peer groups based on comparative advantage. Two key results emerge: First, when comparative advantage is the guiding principle of peer group organization, the effect of moving a student into an environment with...

This paper estimates social effects of incentivizing people in teams. In two field experiments featuring exogenous team formation and opportunities for repeated social interactions, we find large team effects that operate through social channels. The team compensation system induced agents to...

Scholars have pointed to ethnic and other social divisions as a leading cause of economic underdevelopment, due in part to their adverse effects on public good provision and collective action. We investigate this issue in post-war Sierra Leone, one of the world's poorest countries. To address...

This paper focuses on the relationship between public action and access to public goods. It begins by developing a simple model of collective action which is intended to capture the various mechanisms that are discussed in the theoretical literature on collective action. We argue that several of...

Collective action to remedy the losses of open access to common-pool resources often is late and incomplete, extending rent dissipation. Examples include persistent over-exploitation of oil fields and ocean fisheries, despite general agreement that production constraints are needed. Transaction...

We estimate the role of benefits and peer effects in technology adoption using data from randomized distribution of menstrual cups in Nepal. Using individual randomization, we estimate causal effects of peer exposure on adoption; using differences in potential returns we estimate effects of...