There is no universally accepted explanation for why crime rates are falling, Many proposed explanations (such as increased
incarceration rates or the
use of leaded gasoline) have only occurred in specific countries, and cannot explain the decrease in other countries. Air pollution has been found to highly correlate with increased aggression and higher crime rates with one study detailing that a 10% reduction in
PM2.5 and
ozone could result in $1.8billion in crime reduction. Multiple hypotheses have been developed to ascertain whether it is due to the aesthetic impact of air pollution which reduces ethicality or some biological factor related to PM2.5 and ozone exposure
neurotoxicity. This may be correlated to the observed loss of
IQ points in children who are heavily exposed to air pollution.
Demographics Another explanation proposes that the international homicide decline is partially a consequence of the aging of populations around the world, which is causing a reduction in the size of the youth relative to other age groups. Since youth tend to commit the majority of violent crimes, and since older members of societies tend to be the more orderly and peaceful, as populations grow older their violence rates tend to decline. However, the most violent countries are not yet enjoying the pacifying benefits of the aging of their populations because other strong criminogenic forces are interfering with their homicide trends.
Abortion Freakonomics coauthor
Steven Levitt posited that the drop in violent crime in the United States correlates with the legalization of abortion in the Supreme Court ruling on
Roe v. Wade in 1973, due to fewer children being born to parents who were unwilling or unable to care for them. Therefore, the theory argues that with fewer children being affected by 'broken homes' the effect was to produce more well adjusted children and when they matured, they wouldn't cause as much crime. However, there is also research which disputes this theory.
Drug use and demand Alfred Blumstein argues that part of the drop in the United States' violent crime rate is due to declining demand for
crack cocaine. A 2014 report by the
Home Office stated that changes in demand for illegal drugs (specifically, heroin) were a major contributor to the crime drop in the United Kingdom.
Economic factors The mainstream view among criminologists is that unemployment and poverty are strongly related to crime, because a decrease in opportunities for legal employment, in theory, should increase the frequency of illegal employment. Multiple studies of the United States, for example, have found that the improvement of the American economy coincided with a drop in crime throughout the 1990s. A 2015 Brennan Center for Justice report, however, estimated that no more than 5 percent of the 1990s crime drop in the United States was attributable to changes in unemployment. The view that higher unemployment rates cause higher crime rates has also been challenged by the fact that the United States crime rate reached a 40-year low in 2010, despite America's lagging economy.
Incarceration A 2004 study found that 58 percent of the drop in violent crime during the 1990s was due to incarceration. A 2015
Brennan Center for Justice report found that increased incarceration was responsible for about 5% of the crime drop in the United States during the 1990s, and for essentially none of the crime drop there since 2000. In 2009,
Steven Messner and
Richard Rosenfeld found that incarceration was negatively related to burglary rates "...only after unusual policy interventions, such as Italy's 2006 clemency measure that dramatically reduced the size of its prison population."
Policing Some have proposed that changes in policing practices (e.g. the adoption of
broken windows policing) were responsible for the crime drop in the United States, especially in New York City. However, Canada did not change its policing practices significantly prior to their crime drop, which casts doubt on the extent to which policing was responsible for this phenomenon. Levitt (2004) estimates that increases in the number of police accounted for between 5 and 6% of the crime drop in the United States during the 1990s. A 2007 study found that misdemeanor arrests were negatively associated with changes in total homicide rates in New York City.
Security hypothesis A 2014 article in
Crime and Justice reported that the "security hypothesis" was the best explanation for the drop out of the 17 hypotheses tested. Consistent with this hypothesis, attempted crime has also been declining, suggesting that would-be criminals are becoming discouraged by improved security.
Combinations Blumstein & Wallman (2006) conclude that a complex interaction between "prisons, drugs, guns, policing, economics," and "demography, including abortion" is the best explanation for the crime drop in the United States.
Francis Fukuyama proposed the following account for the crime increase between the 1950s and the 1990s: postwar economic expansions produced prosperous and peaceable years in the 1950s. However, in short order came
decolonization of most of Africa, much of the Caribbean, and parts of South America and the Middle East; the
Vietnam War and
youthful rebellions of the 1960s; the
civil,
women's, and
gay rights movements; economic transformations including the
OPEC oil embargoes of the 1970s, massive economic restructuring, and
globalization; and vastly increased
movements of people between countries. Fukuyama argues, in retrospect this has been all too much to be absorbed in a short time. ==See also==