Costa Rica ranked number three out of 163 nations in the 2010 Environmental Performance Index (EPI), a biannual ranking system that is produced by Yale University and Columbia University. The index, released Thursday, gauges a country's “environmental health” and “ecosystem viability,” and scored nations in 10 policy categories that are divided into 25 environmental indicators.

The aggregate categories include analysis of each nation's performance in limiting greenhouse gas emissions, water management, forestry and biodiversity, to name a few, and build on information gathered before 2009 from international organizations, universities and the United Nations.

Costa Rica scored 86.4 percent overall and ranked behind Switzerland, at 89.1 percent, and Iceland, at 93.5 percent.

In a press release, analysts indicated that the 2010 rankings suggest that income is a major determinant of environmental success.

“Chile, where substantial investments in environmental protection have been made, ranks 16th while its neighbor, Argentina, which has done much less to improve its pollution control and natural resource management, lags in 70th place,” the release states.

By comparison, Nicaragua and Panama, Costa Rica's two neighboring nations, ranked 93rd and 24th, respectively. The United States came in 61st place.

Experts acknowledged, however, that data gaps existed in the information they used for the index. Many of the statistics came from questionable government reporting, which in some cases “are not subject to any external review.”

“High quality data combined with appropriate statistical analysis can certainly help policymakers identify problems and trends,” said Jay Emerson, a statistics professor at Yale. “Conclusions that emerge are only as good as the underlying data.”

Costa Rica climbed from number five in 2008 and number 15 in 2006, the first year the indicator was published.