The United States Peace Index (USPI) provides a comprehensive measure of US peacefulness dating back to 1991.

It also provides an analysis of the socio-economic measures that are associated with peace as well as estimates of the costs of violence and the economic benefits that would flow from increases in peace. This is the second edition of the USPI.

In this report, a Metropolitan Peace Index has also been produced which measures the peacefulness of 61 metropolitan statistical areas within the US.

The USPI is based on the work of the Global Peace Index, the preeminent global measure of peacefulness, which has been produced by the Institute of Economics and Peace (IEP) every year since 2007.

– The U.S. is now more peaceful than at any time in the last 20 years. This has been driven by a steady decrease in the homicide and violent crime rates combined with recent modest decreases in the incarceration rate.

– There were improvements in all indicators from the 2011 to the 2012 Index. The homicide rate decreased by 3.78%, the violent crime rate fell 6.03%, and the total number of state prisoners fell by 0.6%. There were also slight reductions in the number of police employees and the number of firearm suicides as a percentage of total suicides, which suggests a fall in gun ownership.

– Maine is the most peaceful state in the U.S. for the 11th year in a row, Louisiana is the least peaceful. The Northeast continues to be the most peaceful region with three of the five most peaceful states. The South is once again the least peaceful region in America, with four of the five least peaceful states. For the 20th year in a row, Louisiana is the least peaceful state.

– There are significant economic benefits from improving peacefulness. Violence and violence containment cost the average taxpayer $3,257 each year. If all the states in the U.S. had the same level of peacefulness as the most peaceful state (Maine), the total economic effect would be over 274 billion dollars.

– The level of direct violence has decreased dramatically in the last 20 years. The homicide rate has decreased by over 50% since 1991, and there have been similar reductions in the rate of assaults, rapes, and robberies. Violent crime has decreased every single year except one in the last 20 years.

– The prison population has decreased for the second year running. The prison population appears to have peaked and a new trend is emerging where incarceration rates are falling. This has largely been driven by a combination of falling crime rates and budget constraints.

– The drop in officially recorded violence has been partially offset by increases in violence in prison. The explosive growth of the prison population in the U.S. has resulted in a purported epidemic of prison assault and rape. If this prison violence is included in USPI calculations, the decline in the total level of violence is smaller.

– Peace is linked to economic opportunity, health, education, and social capital. The 2011 USPI found a strong correlation between peace and a number of secondary factors, which has been reinforced by the 2012 USPI.

– More peaceful states tend to have more economic opportunities, better provision of basic services and higher levels of educational attainment. In addition, the 2012 USPI has found there is a strong correlation between social capital and peace. More peaceful states tend to have more social capital which represents a better sense of community, and higher rates of volunteerism.

– Cambridge-Newton-Framingham in Massachusetts is the most peaceful metropolitan area in America.

– Detroit-Livionia-Dearborn is the least peaceful metropolitan area in the U.S.