ST. LEONARDS, Australia, May 20 (UPI) -- The United States and Russia are in the bottom half of an annual study ranking nations on how peaceful they are, surveyors said Tuesday.

Iceland topped Vision of Humanity's Global Peace Index of 140 countries that analyzes how peaceful they are regarding international policy and domestic conditions, The Financial Times reported Tuesday.

Because of continued violence since the 2003 U.S.-led invasion, Iraq ranked last in the index developed by the organization based in Australia.

The survey found 16 of the 20 most peaceful states are European democracies, most of them European Union members. China ranked 67th; the United States, 97th, and Russia, 131st.

The Global Peace Index was developed by the think-tank Institute for Economics and Peace and the Economist Intelligence Unit. It ranks each nation using 24 "peacefulness" measurements, including a nation's relations with its neighbors, arm sales and troop deployments.

Index officials said the United States' position reflects its military expenditures and engagement. It also has more citizens in jail than any other nation, proportionally.

Iceland's ranking reflects its political stability and its good relations with its neighbors, the index indicated. Iceland has no standing army and proportionally, has among the lowest percentage of its citizens incarcerated.