INTRODUCTION I. THE DEATH PENALTY'S RECENT HISTORY IN THE UNITED STATES II. THE CONFLICT IN PREVIOUS STUDIES ON CAPITAL PUNISHMENT AND DETERRENCE A. Early Literature on Capital Punishment and Deterrence B. Modern Studies of Capital Punishment's Deterrent Effect 1. Modern Economics Papers Using Panel-Data Techniques 2. Modern Economics Papers Using Other Techniques 3. Modern Papers by Sociologists and Criminologists. 4. Modern Papers in Law Reviews 5. A Theory for Reconciling the Results III. TESTING THE DETERRENCE HYPOTHESIS AMONG STATES A. Differences in the Application of Capital Punishment across States B. Data and Empirical Model 1. A Summary of the Model 2. The Model's Technical Structure 3. The Model's Details 4. The Model's Six Variations C. Empirical Results D. Reconciliation with Other Papers IV. A THRESHOLD EFFECT HELPS TO EXPLAIN CAPITAL PUNISHMENT'S DIFFERING IMPACTS ACROSS STATES A. Summary Statistics 1. Amount of Capital Punishment 2. Publicity 3. Characteristics of Executed Persons 4. Method of Execution 5. The Threshold Effect B. Regression Results 1. Spline Regression 2. Dummy-Variable Regressions C. Explaining Brutalization, Deterrence, and the Threshold Effect V. OTHER MODELS A. State-Level Monthly Data: 1977-1999 B. State-Level Annual Data: 1960-2000 CONCLUSION APPENDIX INTRODUCTION
Recent empirical studies by economists have shown, without exception, that capital punishment deters crime. Using large data sets that combine information from all fifty states over many years, the studies show that, on average, an additional execution deters many murders. The studies have received much publicity, and death penalty advocates often cite them to show that capital punishment is sound policy.
Indeed, deterrence is the central basis that many policymakers and courts cite for capital punishment. For example, President Bush believes that capital punishment deters crime and that deterrence is the only valid reason for capital punishment. (1) Likewise, the Supreme Court, when it held in its landmark 1976 decision that capital punishment was constitutional, cited deterrence as one of its main reasons. (2) Moreover, the Court confirmed that the main factor that motivated most state legislatures to prescribe capital punishment was deterrence. (3) Similarly, a central issue in debates on whether federal law should include capital punishment is deterrence. (4) We can also reasonably assume that juries and trial judges, in deciding whether to impose or overturn death sentences, will incorporate common understandings about deterrence. Governors may be similarly influenced in making decisions about clemency.
In contrast to the economic studies, recent studies by sociologists and law professors have reached an opposite conclusion. The studies are often restricted to a single state or small group of states rather than economists' examination of the average for the nation as a whole. They usually find no deterrence. Death penalty opponents cite these studies.
Each group tends to ignore the other's research. In this paper, I reconcile the results and show that both conclusions can be correct.
Using the same large data set of U.S. counties from 1977 to 1996 that many other crime studies use (and that I used in one of my earlier studies), I change the focus from national averages for deterrence. (5) Instead, I examine whether capital punishment's impacts on murder rates differ among states.
The results are striking. Consider the twenty-seven states where at least one execution occurred during the sample period. Executions deter murder in only six states. Capital punishment, however, actually increases murder in thirteen states, more than twice as many as experience deterrence. In eight states, capital punishment has no effect on the murder rate. That is, executions have a deterrent effect in only twenty-two percent of states. In contrast, executions induce additional murders in forty-eight percent of states. In seventy-eight percent of states, executions do not deter murder.
I then explore why these differences exist among states. After investigating various possible explanations, I identify an important factor (although other factors are also undoubtedly important): on average, the states where capital punishment deters murder execute many more people than do the states where capital punishment incites crime or has no effect. Using various statistical techniques, I show that a threshold number of executions for deterrence exists, which is approximately nine executions during the sample period. In states that conducted more executions than the threshold, executions, on average, deterred murder. In states that conducted fewer executions than the threshold, the average execution increased the murder rate or had no effect.
An intuitive explanation is that each execution has two opposing effects. First, the execution creates a brutalization effect: it contributes to creating a climate of brutal violence. The execution sets an example of killing to avenge grievances, an example that some private individuals then follow. Second, the execution creates some deterrence: potential criminals recognize that the state is willing to wield the ultimate penalty. For the first few executions, however, the deterrent effect is small. Only if a state executes many people does deterrence grow; only then do potential criminals become convinced that the state is serious about the punishment, so that the criminals start to reduce their criminal activity. When the number of executions exceeds the threshold, the deterrence effect begins to outweigh the brutalization effect. In the seventy-eight percent of states where executions either increase murders or have no effect, the brutalization effect either counterbalances or outweighs the deterrent effect. The deterrent effect outweighs the brutalization effect only in six states.
The results suggest that earlier economic papers' focus on national averages masked variation among states. Because the six states with deterrence, such as Texas, execute many people, the executions in these states deter many murders. In contrast, most of the states where executions increase murder execute few people. When the large number of executions in the deterrence states are averaged in with the small number of executions in all of the other states, the large deterrent effect in those states dominates the opposite brutalization effect in the other states. Thus the result from earlier economics papers: on average, an execution in the United States deters crime. This paper shows that these averages are powered by a handful of high-execution, high-deterrence states. In most states, capital punishment either increases murder or has no effect.
The results also explain the findings of no deterrence in papers that have focused on individual states, rather than on the nation as a whole. As the results here show, in seventy-eight percent of states, executions do not deter murder.
All of the primary models' general lessons are consistent across two other models that use data from other time periods and with different levels of aggregation.
This Article's results have two important policy implications. First, policymakers' false beliefs about capital punishment's universal deterrent effect may have caused many people to die needlessly. If deterrence is capital punishment's purpose, as is often stated by our president and others, then, in the majority of states where executions do not deter crime, executions kill convicts uselessly. Moreover, in the many states where the brutalization effect outweighs the deterrent effect, executions not only kill convicts needlessly but also induce the additional murders of many innocent people. A very rough estimate is that, all told from 1977 to 1996, executions in no-deterrence states have killed more than 5,000 innocent people, or 250 per year. Thus, in the many states that execute without a deterrent effect, policymakers should consider abandoning the death penalty. These states' executions do not deter crime. If deterrence is the goal, capital punishment in these states simply does not work. Instead, it needlessly kills both convicts and innocents.
Of course, if policymakers in the no-deterrence states have goals other than deterrence, such as retribution, then they might continue capital punishment, despite the absence of deterrence. In the many states, however, where executions not only fail to deter but also cause additional murders of innocent people, policymakers might think twice before permitting state-sponsored revenge that, in effect, kills innocent bystanders.
Second, suppose that a state was considering whether to start executing people. It could not focus only on deterrence, ignoring other important moral, legal, and economic issues. The state would need to recognize that deterrence cannot be achieved with a half-hearted execution program. Unless the state executed enough people to exceed the deterrence threshold, then a large risk would exist that the executions would increase murders. People in many states may be unwilling to establish such a large execution program.
The rest of the Article is organized as follows. After Part II discusses capital punishment's recent history in the United States, Part III reviews the conflict in recent studies on capital punishment and deterrence. Part IV explores differences in states' applications of capital punishment and tests the effect on murder of executions in individual states. In Part V, I examine possible causes of the different effects of executions on murder across states. Part VI then offers results from two other models and data sets. Finally, Part VII presents conclusions.
THE DEATH PENALTY'S RECENT HISTORY IN THE UNITED STATES
During the first half of the twentieth century, executions were both frequent and popular. More executions occurred during the 1930s than in any other decade in U.S. history, an...