Randomized experiments commonly compare subjects receiving a treatment to subjects receiving a placebo. An alternative design, frequently used in field experimentation, compares subjects assigned to an untreated baseline group to subjects assigned to a treatment group, adjusting statistically...

In recent years, social scientists have increasingly turned to matching as a method for drawing causal inferences from observational data. Matching compares those who receive a treatment to those with similar background attributes who do not receive a treatment. Researchers who use matching...

Prior to the November 6, 2001 elections, randomized voter mobilization experiments were conducted in Bridgeport, Columbus, Detroit, Minneapolis, Raleigh, and St. Paul. Names appearing on official lists of registered voters were randomly assigned to treatment and control groups. A few days before...

Political campaigns currently make extensive use of direct mail, particularly in state and local races, yet its effects on voter behavior are not well understood. This essay presents the results of large-scale randomized field experiments conducted in Connecticut and New Jersey during state and...

The debate about the cost-effectiveness of randomized field experiments ignores one of the most important uses of experimental data. This article defines and illustrates "downstream" experimental analysis - that is, analysis of the indirect effects of experimental interventions. We argue that...

We report the results of a randomized field experiment involving approximately 30,000 registered voters in New Haven, Connecticut. Nonpartisan get-out-the-vote messages were conveyed through personal canvassing, direct mail, and telephone calls shortly before the November 1998 election. A...

Missing outcome data plague many randomized experiments. Common solutions rely on ignorability assumptions that may not be credible in all applications. We propose a method for confronting missing outcome data that makes fairly weak assumptions but can still yield informative bounds on the...

Regression discontinuity (RD) designs enable researchers to estimate causal effects using observational data. These causal effects are identified at the point of discontinuity that distinguishes those observations that do or do not receive the treatment. One challenge in applying RD in practice...

This brief review considers how field experiments have contributed to the study of collective action. Field experiments have largely supported findings from laboratory studies suggesting that collective action problems are often overcome through communication and social pressure. These results...

Political partisanship is strongly correlated with attitudes and behavior, but it is unclear from this pattern whether partisan identity has a causal effect on political behavior and attitudes. We report the results of a field experiment designed to investigate the causal effect of party...