Understanding Why Crime Fell in the 1990S: Four Factors That Explain the Decline and Six That Do
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Journalof Economic Perspectives—Volume 18,Number 1—Winter 2004 — Pages163– 190 UnderstandingWhy Crime Fellin the 1990s:Four Factors that Explainthe Declineand Six that DoNot Steven D.Levitt rimefell sharply inthe United States in the 1990s, in all categories of crimeand allparts ofthe nation. Homiciderates plunged 43 percentfrom C thepeak in 1991 to 2001, reaching the lowest levels in 35 years. The FederalBureau of Investigation’s (FBI)violent and propertycrime indexes fell 34 and 29percent, respectively, over that sameperiod. These declines occurred essentiallywithout warning: leadingexperts were predicting an explosionin crime intheearly and mid-1990s,precisely the point when crimerates began to plunge. Although expertsfailed to anticipate the decline, there has beenno shortage ofhypotheses toexplain the drop incrimeafter the fact. Table1 presentsa tallyof aLexis-Nexissearch ofthe most frequently cited reasons forthe crime decline in articlesin major newspapers overthe period 1991– 2001. The single most frequent explanationgiven is the innovative policing strategies put intoplace. Thecrime declineis also frequentlyattributed to increased imprisonment, changes inthe marketfor crack cocaine, theaging of the population, toughergun controllaws, thestrong economy and increasesin the number of police. In this paper, Iattemptto sort out why crimedeclined in the 1990s. I begin witha reviewof the facts. Ithen analyzethe leading explanations forwhy crime fell, lookingat possibledeterminants that changed insome substantial wayin the1990s. Most ofthe supposed explanations listedin Table1 actuallyplayed little direct role inthecrime decline, including the strong economy of the 1990s, changing demo- graphics, betterpolicing strategies, gun controllaws, concealedweapons lawsand increaseduse ofthedeath penalty. Fourfactors, however,can account forvirtually y Steven D.Levittis theAlvin H.Baum Professorof Economics, University of Chicago, and ResearchFellow, AmericanBar Foundation,both in Chicago, Illinois. This article was written whilethe author was a fellowduring the 2002– 2003 academic year atCenter for Advanced Studyin the Behavioral Sciences, StanfordUniversity, Stanford, California. 164Journal of Economic Perspectives Table 1 MediaExplanations for the Decline in Crime in the 1990s,Ranked by Frequencyof Mention Explanation Numberof mentions Innovative policingstrategies 52 Increasedreliance on prisons 47 Changesin crack/ otherdrug markets 33 Agingof the population 32 Toughergun control laws 32 Strongeconomy 28 Increasednumber of police 26 Allother explanations 34 Notes: Basedon a Lexis-Nexissearch of articleswritten aboutthe national declinein crime in leading newspapers over the period 1991–2001. Newspapers included in the tabulationare the New York Times,Washington Post, USA Today, Houston Chronicle, San Francisco Chronicle,Chicago Sun Times, Boston Globe, Atlanta Journal Constitution, MinneapolisStar Tribune and San Diego Union-Tribune. Theseare the ten largestcirculation newspapers that areincluded in Lexis-Nexis. allof the observed decline in crime: increases in thenumber of police, the rising prison population, thewaning crackepidemic and thelegalization of abortion. 1 Thus, Iconclude that thedecline in crimedoes not reallypose apuzzle,but rather, isreadily explained by the available theories. The real puzzle that stands unan- swered,I argue,is whycrime rates did not startfalling earlier. In the nal section, Ioffersome tentative observations about what crimetrends might be expected in thenext decade. Dening Features of the Decline in Crime in the 1990s Severaldifferent aspects ofthedecline in crime are particularly noteworthy: its size,breadth and persistenceacross categoriesof crime; its universality across geographicand demographicgroups; and itsunexpectedness. Iconsiderthese characteristicsin turn. TheMagnitude of the Decline Themost remarkable feature of the crime decline in the United States was its sheermagnitude. Figure 1 presentstime series data forhomicides from 1950 to 1 Reyes(2002) offersan additionalintriguing explanation for the declinein crime:the reductionin levelsof leadin the blooddue to the eliminationof leadedgasoline and lead-basedpaints. Becauseof the highlyspeculative nature ofthe Reyesconjecture at the presenttime, I donot discussthis hypothesis at greaterlength, although it isclearly an areaworthy ofcontinued future research. Steven D.Levitt165 Figure 1 HomicideRate, 1950 –2001 12 s t 10 n e d i s e r 8 0 0 0 , 0 0 1 6 r e p s e 4 d i c i m o H 2 0 1950 1960 1970 1980 1990 2000 2001.Homicide is themost accurately measured and mostserious crime and thus providesa usefulbenchmark. Homiciderates were relatively steady at about 4 –5 per100,000 population from1950 through themid-1960s, at which point they startedrising to a peakof 10.2 per 100,000 population in1980. From 1980 to 1991, thehomicide rate uctuated between8 –10per100,000 population. Afterthat, the homicidetrend began alarge,steady decline.Between 1991 and 2000,homicide ratesper capita fellfrom 9.8 to 5.5 per 100,000, a drop of44 percent. Since that time,homicide rates have beensteady. Thesame pattern observed for homicide is present for every major crime categoryand inboth ofthe commonly used measuresof crime in theUnited States: the FBI’sUniformCrime Reports (UCR), coveringcrimes reported to the police, and theNational Crime Victimization Survey (NCVS), a large,nationally represen- tativephone surveyof Americans. Table 2 reportsthe percentage decline between 1991and 2001.For purposes ofcomparison, thepercentage change incrimerates overthe period 1973 –1991is also shown (1973is the rstyear of availability for NCVS).For the period 1991 –2001,crimes reported to the police fell between 24 and 46percent across thevarious crime categories. The reduction in criminal victimizationsin NCVS is even greater, ranging from 45 to 58 percent. 2 2 Thecongruence between the UCR and NCVSdata forthe 1990sis heartening, giventhat the aggregate trendsin thesetwo data sourceshave failedto track closelyone another historically, as evidencedin the rst columnof the table.Between 1973 and 1991,the UCR data suggestsharply risingcrime in most categories,whereas the victimizationdata nds declinesin crime for more than half ofthe categories. Boggessand Bound(1997) arguethat apartialexplanation for the differentpatterns isthat the twodata sets measuresomewhat different crimes; for example, NCVS crimes tend tobe lessserious, even within acrimecategory. 166Journal of Economic Perspectives Table 2 NationalTrends in Speci cCategoriesof Crime Percentagechange in crime Percentagechange in crime Crimecategory anddata source category,1973 –1991 category,1991 –2001 Crimesreported to the policefrom UCR Violentcrime 182.9 233.6 Homicide 15.4 242.9 Rape 173.4 224.8 Robbery 150.0 245.8 Aggravated assault 1118.1 226.7 Propertycrime 138.2 228.8 Burglary 13.0 240.9 Larceny 156.7 223.2 Motorvehicle theft 149.8 234.6 Criminalvictimizations from NCVS Violentcrime 11.6 250.1 Rape 220.0 245.0 Robbery 215.5 253.3 Aggravated assault 23.9 256.9 Simpleassault 110.7 247.0 Propertycrime 232.0 252.8 Burglary 241.3 255.6 Theft 246.5 251.6 Motorvehicle theft 116.2 258.6 Notes: Allvalues in the tableare percentage changes in crimerates. Entriesin the toppanel of the table arebased on Uniform Crime Report data collectedby the FederalBureau of Investigation. These changesare de nedin termsof victimizationrates percapita. Entriesin the bottompanel are from the NationalCrime Victimization Survey. For violent crime, the reportedvalues are percentage changes in crimeper person age 12 and older.For property crime, the percentagechanges are per household. The calculationsin the tablecorrect for the redesignof NCVS that occurredin 1993. Uniform Crime Report data fromrecent years is available online at http://www.fbi.gov .NCVSdata isavailable from http:// www.ojp. usdoj.gov/bjs . Thedecline in crime has also beenremarkable in its steady persistence. Homiciderates fell in nineof the ten years in the decade of the 1990s, with the only exceptionbeing a minorupward blipin 1992. In theprevious three decades, homicidehad neverfallen for more than threeconsecutive years. Robbery, bur- glaryand larcenyeach fellevery year between 1991 and 2000.Prior to 1991, robbery rateshad fallenin only eight of the preceding 30 years. Thedrop inU.S. crimeappears tobe unusual among countriesof the world, although de nitionaland reportingdifferences across countries,as wellas thepoor qualityof crime statistics in mostcountries other than theUnited States, make such internationalcomparisons dif cult. Barclay,Tavares and Siddique(2001) provide oneof the most careful cross-country comparisons ofcrime trends. That analysis reportsthat homiciderates fell 4 percenton averagein European Union (EU) memberstates between1995 and 1999,a periodover which U.S. homiciderates fell 28percent. Violent crime rose 11 percent on averagein EU countries over that sametime period, compared to 20 percent drops inU.S. violentcrime. Burglary UnderstandingWhy Crime Fell inthe 1990s 167 Table 3 PercentageChanges in Crime Rates for Different Population Groups, 1991–2001 Homicide ViolentCrime PropertyCrime EntireUnited States 242.9 233.6 228.8 Region Northeast 250.0 242.9 241.5 South 244.6 227.3 225.6 Midwest 232.1 231.5 223.3 West 242.7 238.1 232.0 Urban/rural Within MSAs 245.0 236.7 231.7 Citiesoutside MSAs 231.4 218.4 218.1 Rural 235.0 22.9 211.0 City size .250,000 249.2 243.2 236.1 50,000–250,000 241.4 237.5 231.9 ,50,000 234.9 222.7 223.2 Source: FBI UniformCrime