The world is slightly less peaceful than it was a year ago, in part as a consequence of the global recession. But falling military expenditures in the Middle East and shrinking access to small arms in sub-Saharan Africa are two bright spots in an assessment of the world’s broad trends in peace and violence.

Those are among the findings of the 2010 Global Peace Index, the fourth edition of an annual attempt to objectively quantify peace in a large majority of the world’s countries.

New Zealand ranks as the world’s most peaceful country, the survey finds, based on a list of factors ranging from military expenditures (high is bad) and participation in United Nations peacekeeping (high is good) to social unrest and incarceration rates (both are not good).

IN PICTURES: The most and least peaceful nations in the world

Iraq comes in last at 149 out of 149 countries assessed – the same ignominious placement it snagged last year.

And the United States ranks right in the middle at 85, achieving good marks for factors like respect for human rights and relations with neighbors and other countries, but low scores in areas like domestic homicides, military expenditures, and involvement in external conflicts. Given the criteria, the US not surprisingly comes up as “less peaceful” than countries like Austria and Costa Rica, but it also trails Libya, Cuba, and Equatorial Guinea.

“We work with a definition of peace that is not as the opposite of war but the absence of violence,” says Clyde McConaghy, board director of the Institute for Economics and Peace – the Sydney, Australia, think tank that amasses the information behind the Global Peace Index, or GPI. Weighing 23 factors ranging from domestic instability to militarization, the GPI “provides a snapshot of relative peacefulness among nations,” he adds.

A research team of peace-studies experts from around the world uses the compiled information to come up with the index.

The GPI’s conclusion that the world in 2009 was slightly less peaceful than in 2008 is based on the perspective that the global recession has been a catalyst for conditions that lead to violence. The GPI affirms a “correlation between economic prosperity and peacefulness,” Mr. McConaghy says.

Still, he cautions, growing prosperity does not necessarily equate with a rising peace index: Russia has experienced some impressive (though not necessarily equitable) economic growth in recent years, but remains near the bottom of the GPI (No. 143) after a recent downturn, conflict with Georgia, and internal violence concerning Chechnya.

Nor do all countries respond poorly to adverse economic straits. In one of the earliest surveys, Iceland was No. 1, only to fall to No. 4 last year after the country’s financial meltdown led to upheaval and political instability. But this year Iceland rose again, now placing second behind New Zealand.

The GPI’s goal is to demonstrate that simple priorities lead to peace. “Education is a driver of peacefulness,” McConaghy says. “Not so much the quality of education or how much is spent, but just keeping kids in school.”

The GPI also confirms a trend recently noted by other tabulations of world conflicts: While cross-border wars and armed disputes have decreased in recent years, the number of internal conflicts such as civil wars has increased.

Many Americans may be suspicious of any peace index that has their country behind Nicaragua and Rwanda, McConaghy acknowledges. But he reminds observers that gauging peacefulness is not the same as ranking national well-being or happiness, as some surveys do. “Ours is not an airy definition” of peace, but a “technical definition – it’s not a state of mind,” he says.

Why, then, is America’s contribution to the security of other countries not calculated as a plus for peace? McConaghy acknowledges as a “good point” that US troops in South Korea may have stopped North Korea from invading, for example. But, he says, such judgments would push the GPI into making subjective calls.

“We find it almost impossible to judge which troop deployments are right and which are wrong,” he says. “Russian troops in South Ossetia – is that right or wrong? Someone from South Ossetia might very well insist it’s right.”

The US “is an example of a country with complex issues to face,” he says. “So given that, it gets a pretty good score.”

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IN PICTURES: The most and least peaceful nations in the world