<P> Statistics on specific crimes are indexed in the annual Uniform Crime Reports by the Federal Bureau of Investigation (FBI) and by annual National Crime Victimization Surveys by the Bureau of Justice Statistics . In addition to the primary Uniform Crime Report known as Crime in the United States, the FBI publishes annual reports on the status of law enforcement in the United States . The report's definitions of specific crimes are considered standard by many American law enforcement agencies . According to the FBI, index crime in the United States includes violent crime and property crime . Violent crime consists of four criminal offenses: murder and non-negligent manslaughter, rape, robbery, and aggravated assault; property crime consists of burglary, larceny, motor vehicle theft, and arson . </P> <P> In the long term, violent crime in the United States has been in decline since colonial times . The homicide rate has been estimated to be over 30 per 100,000 people in 1700, dropping to under 20 by 1800, and to under 10 by 1900 . </P> <P> After World War II, crime rates increased in the United States, peaking from the 1970s to the early 1990s . Violent crime nearly quadrupled between 1960 and its peak in 1991 . Property crime more than doubled over the same period . Since the 1990s, however, crime in the United States has declined steeply . Several theories have been proposed to explain this decline: </P> <Ol> <Li> The number of police officers increased considerably in the 1990s . </Li> <Li> On September 16, 1994, President Bill Clinton signed the Violent Crime Control and Law Enforcement Act into law . Under the act, over $30 billion in federal aid was spent over a six - year period to improve state and local law enforcement, prisons and crime prevention programs . Proponents of the law, including the President, touted it as a lead contributor to the sharp drop in crime which occurred throughout the 1990s, while critics have dismissed it as an unprecedented federal boondoggle . </Li> <Li> The prison population has rapidly increased since the mid-1970s . </Li> <Li> Starting in the mid-1980s, the crack cocaine market grew rapidly before declining again a decade later . Some authors have pointed towards the link between violent crimes and crack use . </Li> <Li> Legalized abortion reduced the number of children born to mothers in difficult circumstances, and difficult childhood makes children more likely to become criminals . </Li> <Li> Changing demographics of an aging population has been cited for the drop in overall crime . </Li> <Li> Rising income . </Li> <Li> The introduction of the data - driven policing practice CompStat significantly reduced crimes in cities that adopted it . </Li> <Li> The lead - crime hypothesis suggests reduced lead exposure as the cause; Scholar Mark A.R. Kleiman writes: "Given the decrease in lead exposure among children since the 1980s and the estimated effects of lead on crime, reduced lead exposure could easily explain a very large proportion--certainly more than half--of the crime decrease of the 1994 - 2004 period . A careful statistical study relating local changes in lead exposure to local crime rates estimates the fraction of the crime decline due to lead reduction as greater than 90 percent . </Li> <Li> The quality and extent of use of security technology both increased around the time of the crime decline, after which the rate of car theft declined; this may have caused rates of other crimes to decline as well . </Li> <Li> Increased rates of immigration to the United States . </Li> </Ol>

Since the mid 70s in the u.s property crime rates have
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