The world has become less peaceful in the past year as longstanding global conflicts remain unresolved and the United States and other world powers face political instability, an international study finds.

The 12th annual "Global Peace Index" by the Institute for Economics and Peace, an independent non-profit think tank based in Australia, scored 163 independent states and territories according to their levels of peacefulness. It found the world became 0.27 percent less peaceful compared to 2016, with 92 countries deteriorating in peacefulness and just 71 countries improving. The think tank published the index on Wednesday.

The study assessed global peace through three filters: safety and security in society, extent of ongoing domestic or international conflict and the degree of militarization. Researchers considered 23 peace indicators to determine scores, including the number of casualties from terrorism and conflicts in that country, the number of murders per capita and the ratio of military spending to gross domestic product. Each indicator was scored on a 5-point scale.

The Middle East and North Africa remained the world's least peaceful region, and the four most peaceful regions – Europe, North America, Asia-Pacific and South America – all recorded deteriorations.

Contrary to public perception, many countries decreased in militarization. Instead, the study attributed the gradual fall in peacefulness to a range of factors, including "increased terrorist activity, the intensification of conflicts in the Middle East, rising regional tensions in Eastern Europe and northeast Asia, and increasing numbers of refugees and heightened political tensions in Europe and the U.S."

Europe – which has held the position of most peaceful region through each iteration of the index – faced increased political instability, impact of terrorism and perceptions of criminality, as 23 of the 36 European countries lessened in peacefulness. Also, no Nordic countries are more peaceful today than they were in 2008, researchers found.

The U.S. joined six other G20 members – Mexico, South Africa, Saudi Arabia, India, Turkey and Russia – in the group of 50 least peaceful countries in the world.

The U.S. ranked 121st out of 163 in the global assessment, falling from 114th and 103rd in the 2017 and 2016 Global Peace Indexes, respectively. While the U.S. essentially held its rank relative to other countries' movements, its level of peacefulness declined to its lowest since 2011. Researchers largely attributed the drop in score to a hardening in partisanship in American politics – despite a reduced impact from terrorism, as well as Washington's curtailed operations in Iraq and Afghanistan and a gradual reduction in the homicide rate during the past decade.

It's worthwhile to consider a nation's progress in terms of positive peace, or the attitudes, institutions and structures that create and sustain peaceful societies, says Steve Killelea, executive chairman of the Institute for Economics and Peace. And, civil resistance movements and societal responses are often a good indicator of a country's positive peace levels.

"Countries with higher positive peace can absorb much bigger shocks than countries that are weak in positive peace," he says.

That means countries that have the ability to adapt and adjust to challenges – whatever the disagreement or pressure within society may be – are more likely to maintain peace than countries without those adaptive qualities. Such countries "can suppress change but only to a certain point" before violence breaks out, Killelea says.

Iceland topped the listing with the lowest score, making it the most peaceful country and retaining the title it has held since 2008. New Zealand, Austria, Portugal and Denmark round out the top 5.

Meanwhile, Syria, a nation plagued by civil war, was ranked as the least peaceful country for the sixth consecutive year. Afghanistan, South Sudan, Iraq and Somalia scored among the 5 least peaceful.

As the gap widens between the least and most peaceful countries, the global economy is taking a very real hit.

The global economic impact of violence of roughly $14.8 trillion in 2017 was equivalent to 12.4 percent of the world's gross domestic product or nearly $2,000 per person, according to researchers. Violence in the U.S. last year cost Americans nearly $4,500 per person.

The world's most peaceful countries, according to an analysis by the Institute for Economics and Peace:

Country Peace Rank Iceland 1 New Zealand 2 Austria 3 Portugal 4 Denmark 5 Canada 6 Czech Republic 7 Singapore 8 Japan 9 Ireland 10



The world's least peaceful countries:

Country Peace Rank Syria 163 Afghanistan 162 South Sudan 161 Iraq 160 Somalia 159 Yemen 158 Libya 157 Democratic Republic of the Congo 156 Central African Republic 155 Russia 154