CHICAGO (REUTERS) - Singapore is the safest nation to do business, according to global risk management company Pinkerton's new tool to help corporate clients assess threats on a country-by-country basis.

The Pinkerton Risk Index Report, which the Ann Arbor, Michigan-based unit of Securitas AB announced on Tuesday, lists Switzerland as the second-safest country. The United States ranked seventh.

At the other end of the scale, Chad has the highest overall risk, followed by Zimbabwe and Guinea, according to the index, which uses data based on factors including natural disasters, disease, terrorism, social unrest and economic problems.

Pinkerton said its report would take into account 83 different variables to help companies make decisions on relocations, expansions, investment and business travel.

The report could also help insurers determine risk for providing coverage around the world.

Pinkerton President Jack Zahran said terrorist attacks and natural disasters were becoming more frequent, potentially causing widespread disruption to supply chains. "If you look at how our clients are operating, they're more global, and things are more connected," Mr Zahran said in an interview. "You can't just look at your country in a silo anymore because things happening around the world are going to start impacting you directly and indirectly."

Pinkerton will publish an overall risk index annually, which covers more than 60 countries, while clients can receive daily updates.

Jeff Spivey, president of Security Risk Management Inc and co-founder of the Global Security Risk Management Alliance, said the index could provide companies with more visibility to help them manage risk.

"The companies that have better risk management programs like this make more money," Mr Spivey said, "and they're more profitable, successful companies."