In his Scientific American magazine article entitled, “The Case of the Unsolved Crime Decline,” criminologist Richard Rosenfeld examines why U.S. crime rates dropped more than 40% in the 1990’s and what lessons current policy-makers can learn from this decline. Rosenfeld provides an overview and evaluation of previous research showing a link in the crime rate decline and factors such as changes in demographics, law-enforcement practices, economic conditions, incarceration rates, domestic violence and firearm policies, and the use of guns by young drug dealers. He concludes that while each of these may have contributed toward the decline in serious violent and property crime rates, some of the policies also produced unintended policy effects that could have been avoided if research-based policy experiments had been conducted. For example, stiffer sentences for adult drug offenders, a policy designed to deter crime, may actually facilitate the criminal careers and shorten the lives of the youthful drug sellers who take their place. Based on his research, Rosenfeld provides three lessons that he believes society can draw that may help anticipate and even head off the next crime rate rise. These lessons include dividing crime trends into their component parts, looking for unintended policy effects and engaging in research-based policy experiments before new programs are implemented. (Scientific American, February 2004) See Deterrence. See also, Resources.