The 1990s were a period of unprecedented crime decline in the United States. Yet despite countless fewer victims and savings of law enforcement agencies, little is understood about the causes of the decline. The decline was broad, spanning the seven FBI index crimes: homicide, rape, robbery, aggravated assault, burglary, auto theft, and larceny. It lasted longer than any other crime decline since 1950, when national crime data became available and credible. Over the course of the decline, crime dropped further than ever before: homicides, a crime that can be measured accurately through coroner reports, decreased 39%. Decreases of similar magnitude were experienced in the other index crimes. (See figure 1.2 below.) University of California Criminologist Franklin Zimring, one of the leading authorities in the field, examines the historical origins of the crime decline, the state of the research, and the lessons for the future in his newest book, The Great American Crime Decline (Oxford University Press, 2007).
Professor Zimring’s conclusions are a reminder of the limitations of current theories to explain and predict crime trends. In his thorough examination of the relevant research and literature in criminology, Zimring finds that no theory fully explains the historical crime trends with a reasonable degree of confidence, and that no theory of the causes of crime provides more than the roughest prediction of future crime trends. Zimring’s strongest critique of theories to explain the great American crime decline in the 1990s is based on his comparison of the experiences of the United States and Canada. Canada experienced a decrease in crime similar in time, magnitude, and breadth as the United States but without many of the factors assumed to be the causes of the decline in the United States. (See figure 5.1 below.)
Zimring presents three explanations for the crime decrease in the 1990s that he finds credible. First, the dramatic increase in the imprisonment rates in the US, which began in 1973 and continues at the present. The total population of prison inmates in the United States increased from 110,000 in 1980 to 1,540,000 in 2000. With high imprisonment rates, incapacitation increases, putting downward pressure on crime rates. However, Canada’s imprisonment rates remained completely flat through the same period, while it experienced a similar decrease in crime. (See figure 5.17 below.)
The economic expansion during the 1990s is the second credible explanation for the American crime decline. Several theories link crime with the state of the economy. The eight year period from 1992 to 2000 was America’s longest economic expansion in the 20th century. Despite this unambiguous economic growth, statistical measurements of the effect of the expansion on crime are mixed, with some studies concluding that the growing economy had a small effect and others attributing up to 40% of the decline in property crime to the expanding economy. However, the...