Global political risk is decreasing, according to Aon.

Thirteen countries have been upgraded on this year’s Political Risk Map, meaning their risk rating is lower than last year. Only three countries were upgraded in 2012.

Twelve countries have been downgraded compared with 21 last year.

It follows several years in which downgrades outnumbered upgrades, with the Arab Spring, the global financial crisis and unease in south Asia taking their toll.

This year’s upgraded countries are Armenia, Azerbaijan, Bahrain, Barbados, Belarus, Guatemala, Macedonia, Montenegro, Oman, Pakistan, Swaziland, Thailand and the UAE.

Downgraded countries are Algeria, Cameroon, Chad, Ethiopia, Madagascar, Mali, Namibia, Moldova, Turkmenistan, Uzbekistan, Panama and Paraguay.

Improvements in central Asia and the fringes of Europe reflect structural reform to attract investment.

Cameroon, Chad, Mali and Algeria have been destabilised by regime changes in north Africa, Aon says. The flow of weapons and insurgents across borders has exacerbated political risk and further downgrades are possible.

Aon measures political risk in 163 countries to assess threats associated with exchange transfers, sovereign non-payment, political interference, supply chain disruption, legal and regulatory regimes, political violence, ease of business, banking sector vulnerability and governments’ capability to provide fiscal stimulus.

Countries receive a risk rating from low to very high. Members of the EU and the Organisation for Economic Co-operation and Development are not rated.