Most Popular Books by Steven D. Levitt

''A HUMDINGER'' THE TIMES BIGGER, BETTER AND MORE CONTROVERSIAL, THE INTERNATIONALLY BESTSELLING FREAKQUEL IS HERE IN A SUPER-DELUXE, SUPER-ILLUSTRATED EDITION. Steven Levitt, the original rogue economist, and Stephen Dubner look deeper, question harder and uncover even more hidden truths about our world, from terrorism to shark attacks, cable TV to hurricanes. They ask, among other things- What''s a sure-fire way to catch a terrorist? Are people hard-wired for altruism or selfishness? Which cancer does chemotherapy work best for? Why is saving the planet easier than we think? With this illustrated edition, Levitt and Dubner bring alive their unique analysis and storytelling with an explosion of visual evidence to reveal the world in a bold, new way. Seeing is believing . . .

It is typically difficult to differentiate empirically between deterrence and incapacitation since both are a function of expected punishment. In this paper we demonstrate that the introduction of sentence enhancements (i.e. increased punishments that are added on to prison sentences that would have been served anyway) provides a direct means of measuring deterrence. Because the criminal would have been sentenced to prison anyway, there is no additional incapacitation effect from the sentence enhancement in the short-run. Therefore, any immediate decrease in crime must be due to deterrence. We test the model using California''s Proposition 8 which imposed sentence enhancements for a selected group of crimes. In the year following its passage, crimes covered by Proposition 8 fell by more than 10 percent relative to similar crimes not affected by the law, suggesting a large deterrent effect. Three years after the law comes into effect, eligible crimes have fallen roughly 20-40 percent compared to non-eligible crimes. This large deterrent effect suggests that sentence enhancements, and may be more cost-effective than is generally thought.

We present the results of a novel early childhood intervention in which disadvantaged 3-4-year- old children were randomized to receive a new preschool and parent education program focused on cognitive and non-cognitive skills (CogX) or to a control group that did not receive preschool education. In addition to a typical academic year (9 month) program, we also evaluated a shortened summer version of the program (2 months) in which children were treated immediately prior to the start of Kindergarten. Both programs, including the shortened version, significantly improved cognitive test scores by about one quarter of a standard deviation relative to the control group at the end of the year. The shortened version of the program was equally as effective as the academic- year program because most of the gains in the academic-year program occurred within the first few months.

Japanese edition of Think Like a Freak: The Authors of Freakonomics Offer to Retrain Your Brain. This follow up of the bestselling and amazingly easy to comprehend books on economics, the Freakonomics series, again helps readers approach life in a more out of the box and creative way. In Japanese. Annotation copyright Tsai Fong Books, Inc. Distributed by Tsai Fong Books, Inc.

Hurricane Katrina destroyed more than 200,000 homes and led to massive economic and physical dislocation. Using a panel of tax return data, we provide one of the first comprehensive analyses of the hurricane''s long-term economic impact on its victims. Katrina had large and persistent impacts on where people live; small and mostly transitory impacts on wage income, employment, total income, and marriage; and no impact on divorce or fertility. Within just a few years, Katrina victims'' incomes fully recover and even surpass that of controls from similar cities that were unaffected by the storm. The strong economic performance of Katrina victims is particularly remarkable given that the hurricane struck with essentially no warning. Our results suggest that, at least in this particular disaster, aid to cover destroyed assets and short-run income declines was sufficient to make victims financially whole. Our results provide some optimism regarding the costs of climate-change driven dislocation, especially when adverse events can be anticipated well in advance.

The number of prisoners incarcerated on drug-related offenses rose fifteen-fold between 1980 and 2000. This paper provides the first systematic empirical analysis of the implications of that dramatic shift in public policy. We show that the increase in drug prisoners led to reductions in expected time served for other crimes, especially for less serious offenses. Reductions in time served, however, increased other crimes by no more than a few percent. Moreover, incarcerating drug offenders is found to be almost as effective in reducing violent and property crime as locking up other types of offenders. We estimate that cocaine prices are 10-15 percent higher today as a consequence of increases in drug punishment since 1985. Based on previous estimates of the price elasticity of demand for cocaine, this implies a reduction in cocaine consumed of as much as 20 percent

School choice has become an increasingly prominent strategy for urban school districts seeking to enhance academic achievement. Evaluating the impact of such programs is complicated by the fact that a highly select sample of students takes advantage of these programs. To overcome this difficulty, we exploit randomized lotteries that determine high school admission in the Chicago Public Schools. Surprisingly, we find little evidence that attending sought after programs provides any benefit on a wide variety of traditional academic measures, including standardized test scores, attendance rates, course-taking, and credit accumulation. This is true despite the fact that those students who win the lotteries attend better high schools along a number of dimensions, including higher peer achievement levels, higher peer graduation rates, and lower levels of poverty. We do, however, uncover evidence that attendance at such schools may improve a subset of non-traditional outcome measures, such as self-reported disciplinary incidences and arrest rates.

In most settings, it is difficult to measure discrimination, and even more challenging to distinguish between competing theories of discrimination (taste-based versus information-based). Using contestant voting behavior on the television game show Weakest Link, one can in principle empirically address both of these questions. On the show, contestants answer questions and vote off other players, competing for a winner-take-all prize. In early rounds, strategic incentives encourage voting for the weakest competitors. In later rounds, the incentives reverse, and the strongest competitors become the logical target. Controlling for other observable characteristics including the number of correct answers thus far, both theories of discrimination predict that in early rounds, excess votes will be made against groups targeted for discrimination. In later rounds, however, taste-based models predict continued excess votes, whereas statistical discrimination predicts fewer votes against the target group. Empirically, I find some evidence of information-based discrimination towards Hispanics (i.e., other players perceive them as having low ability) and taste-based discrimination against older players (i.e., other players treat them with animus). There is little in the data to suggest discrimination against women and Blacks

This paper demonstrates that rising crime rates in cities are correlated with city depopulation. Instrumental variables estimates, using measures of the certainty and severity of a state?s criminal justice system as instruments for city crime rates, imply that the direction of causality runs from crime to urban flight. Using annual city-level panel data, our estimates suggest that each additional reported crime is associated with a one person decline in city residents. There is some evidence that increases in suburban crime tend to keep people in cities, although the magnitude of this effect is small. Analysis of individual-level data from the 1980 census confirms the city-level results and demonstrates that almost all of the crime-related population decline is attributable to increased outmigration rather than a decrease in new arrivals to a city. Those households that leave the city because of crime are much more likely to remain within the SMSA than those leaving the city for other reasons. The migration decisions of high-income households and those with children are much more responsive to changes in crime than other households. Crime-related mobility imposes costs on those who choose to remain in the city through declining property values and a shrinking tax base.

"This paper describes basic facts regarding the black-white test score gap over the first four years of school. Black children enter school substantially behind their white counterparts in reading and math, but including a small number of covariates erases the gap. Over the first four years of school, however, blacks lose substantial ground relative to other races; averaging .10 standard deviations per school year. By the end of third grade there is a large Black-White test score gap that cannot be explained by observable characteristics. Blacks are falling behind in virtually all categories of skills tested, except the most basic. None of the explanations we examine, including systematic differences in school quality across races, convincingly explain the divergent academic trajectory of Black students"--National Bureau of Economic Research web site.

This study presents an overview of modern field experiments and their usage in economics. Our discussion focuses on three distinct periods of field experimentation that have influenced the economics literature. The first might well be thought of as the dawn of quot;fieldquot; experimentation: the work of Neyman and Fisher, who laid the experimental foundation in the 1920s and 1930s by conceptualizing randomization as an instrument to achieve identification via experimentation with agricultural plots. The second, the large-scale social experiments conducted by government agencies in the mid-twentieth century, moved the exploration from plots of land to groups of individuals. More recently, the nature and range of field experiments has expanded, with a diverse set of controlled experiments being completed outside of the typical laboratory environment. With this growth, the number and types of questions that can be explored using field experiments has grown tremendously. After discussing these three distinct phases, we speculate on the future of field experimental methods, a future that we envision including a strong collaborative effort with outside parties, most importantly private entities.

We document and analyze the emergence of a substantial gender gap in mathematics in the early years of schooling using a large, recent, and nationally representative panel of children in the United States. There are no mean differences between boys and girls upon entry to school, but girls lose more than two-tenths of a standard deviation relative to boys over the first six years of school. The ground lost by girls relative to boys is roughly half as large as the black-white test score gap that appears over these same ages. We document the presence of this gender math gap across every strata of society. We explore a wide range of possible explanations in the U.S. data, including less investment by girls in math, low parental expectations, and biased tests, but find little support for any of these theories. Moving to cross-country comparisons, we find that earlier results linking the gender gap in math to measures of gender equality are sensitive to the inclusion of Muslim countries, where in spite of women''s low status, there is little or no gender gap in math.

The minimax argument represents game theory in its most elegant form: simple but with stark predictions. Although some of these predictions have been met with reasonable success in the field, experimental data have generally not provided results close to the theoretical predictions. In a striking study, Palacios-Huerta and Volij (2007) present evidence that potentially resolves this puzzle: both amateur and professional soccer players play nearly exact minimax strategies in laboratory experiments. In this paper, we establish important bounds on these results by examining the behavior of four distinct subject pools: college students, bridge professionals, world-class poker players, who have vast experience with high-stakes randomization in card games, and American professional soccer players. In contrast to Palacios-Huerta and Volij''s results, we find little evidence that real-world experience transfers to the lab in these games--indeed, similar to previous experimental results, all four subject pools provide choices that are generally not close to minimax predictions. We use two additional pieces of evidence to explore why professionals do not perform well in the lab: (1) complementary experimental treatments that pit professionals against preprogrammed computers, and (2) post-experiment questionnaires. The most likely explanation is that these professionals are unable to transfer their skills at randomization from the familiar context of the field to the unfamiliar context of the lab.

The Ku Klux Klan reached its heyday in the mid-1920s, claiming millions of members. In this paper, we analyze the 1920s Klan, those who joined it, and the social and political impact that it had. We utilize a wide range of newly discovered data sources including information from Klan membership roles, applications, robe-order forms, an internal audit of the Klan by Ernst and Ernst, and a census that the Klan conducted after an internal scandal. Combining these sources with data from the 1920 and 1930 U.S. Censuses, we find that individuals who joined the Klan were better educated and more likely to hold professional jobs than the typical American. Surprisingly, we find few tangible social or political impacts of the Klan. There is little evidence that the Klan had an effect on black or foreign born residential mobility, or on lynching patterns. Historians have argued that the Klan was successful in getting candidates they favored elected. Statistical analysis, however, suggests that any direct impact of the Klan was likely to be small. Furthermore, those who were elected had little discernible effect on legislation passed. Rather than a terrorist organization, the 1920s Klan is best described as a social organization built through a wildly successful pyramid scheme fueled by an army of highly-incentivized sales agents selling hatred, religious intolerance, and fraternity in a time and place where there was tremendous demand.

The "Hawthorne effect," a concept familiar to all students of social science, has had a profound influence both on the direction and design of research over the past 75 years. The Hawthorne effect is named after a landmark set of studies conducted at the Hawthorne plant in the 1920s. The first and most influential of these studies is known as the "Illumination Experiment." Both academics and popular writers commonly summarize the results as showing that every change in light, even those that made the room dimmer, had the effect of increasing productivity. The data from the illumination experiments, however, were never formally analyzed and were thought to have been destroyed. Our research has uncovered these data. We find that existing descriptions of supposedly remarkable data patterns prove to be entirely fictional. There are, however, hints of more subtle manifestations of a Hawthorne effect in the original data.

We can think of no question more fundamental to experimental economics than understanding whether, and under what circumstances, laboratory results generalize to naturally occurring environments. In this paper, we extend Levitt and List (2006) to the class of games in which financial payoffs and ''doing the right thing'' are not necessarily in conflict. We argue that behaviour is crucially linked to not only the preferences of people, but also the properties of the situation. By doing so, we are able to provide a road map of the psychological and economic properties of people and situations that might interfere with generalizability of laboratory result from a broad class of games.

We develop a simple algorithm for detecting exam cheating between students who copy off one another''s exam. When this algorithm is applied to exams in a general science course at a top university, we find strong evidence of cheating by at least 10 percent of the students. Students studying together cannot explain our findings. Matching incorrect answers prove to be a stronger indicator of cheating than matching correct answers. When seating locations are randomly assigned, and monitoring is increased, cheating virtually disappears.

A wide range of social indicators turned sharply negative for Blacks in the late 1980s and began to rebound roughly a decade later. We explore whether the rise and fall of crack cocaine can explain these patterns. Absent a direct measure of crack cocaine''s prevalence, we construct an index based on a range of indirect proxies (cocaine arrests, cocaine-related emergency room visits, cocaine-induced drug deaths, crack mentions in newspapers, and DEA drug busts). The crack index we construct reproduces many of the spatial and temporal patterns described in ethnographic and popular accounts of the crack epidemic. We find that our measure of crack can explain much of the rise in Black youth homicides, as well as more moderate increases in a wide range of adverse birth outcomes for Blacks in the 1980s. Although our crack index remains high through the 1990s, the deleterious social impact of crack fades. One interpretation of this result is that changes over time in behavior, crack markets, and the crack using population mitigated the damaging impacts of crack. Our analysis suggests that the greatest social costs of crack have been associated with the prohibition-related violence, rather than drug use per se.

Abstract: In determining the legality of online poker â?? a multibillion dollar industry â?? courts have relied heavily on the issue of whether or not poker is a game of skill. Using newly available data, we analyze that question by examining the performance in the 2010 World Series of Poker of a group of poker players identified as being highly skilled prior to the start of the events. Those players identified a priori as being highly skilled achieved an average return on investment of over 30 percent, compared to a -15 percent for all other players. This large gap in returns is strong evidence in support of the idea that poker is a game of skill.