Many individuals interested in the EPI have asked why some nations have been excluded from our rankings. Did we hand pick the 132 countries that were included in the 2012 Environmental Performance Index (EPI)? Were they selected based on some standard for data quality? Why leave some countries out of a worldwide ranking?

We’d like a complete picture of environmental performance on our planet.

The construction of a composite index requires data from a multitude of sources. Some of these sources have data for every nation, but others have country coverage that is not nearly so complete. When a nation had too many data gaps, we had to make the difficult decision to exclude that nation from the overall EPI ranking. While in the past we addressed data gaps by combining disparate data sources or using imputed or modeled values in some cases, we made a commitment this year to get the most complete and accurate available data.. Therefore, we’d rather leave a nation out of the rankings than give a ranking based on far too little information. But rather than simply close the cases of these missing nations, we’d like to push for efforts that would help us include them next time around.

The first step is to understand the pattern of data coverage: what kinds of nations were commonly excluded?

The fixed costs of data collection and reporting can be high. For many small island nations these costs are simply too big for such small coffers. In addition, in many developing African nations, and countries throughout the globe that have seen political and economic strife, expenditure often focuses first on society’s most immediate needs—the health and survival of the population—and spending on monitoring takes a back seat. In other cases, notably North Korea, data quality and transparency issues resulted in the exclusion of a nation. While it would be desirable to be able to track environmental performance across all countries of the world, data collection and reporting simply cannot be a priority everywhere.

We will soon post all of the data we collected for every country that had data available, regardless of whether they were eventually included in the 2012 EPI to help countries that are missing key data better identify where these gaps occur.

Second, we can understand how the structure of the EPI contributes to the exclusion of some countries: what types of data exhibit better coverage?

There were several indicators that commonly created data coverage issues. In general, these represent difficult data collection methods: household surveys for indoor air pollution and bottom up industry reporting for sulfur dioxide and carbon dioxide emissions. Other indicators had better data coverage and were less likely to exclude a country from the overall rankings by the absence of data. To cite some examples, few countries lacked data for fisheries[1], which were measured via catch data, or for agricultural subsidies based on nominal rates of assistance.

In the future how can we improve country coverage?

There is great opportunity for improving our environmental metrics: finding cost effective and accurate indicators of environmental performance. One potential innovation in this regard is the use of satellite data, incorporated into the 2012 EPI for our fine particulate matter (PM 2.5 )and Forest Loss indicators. In comparison to household surveys that are extremely costly to implement, and self-reported data that can be difficult to verify, satellite data represent a relatively cost-effective solution with little room for manipulation.

It is our hope that future EPIs can include the full range of Earth’s nations with better data.

Ainsley Lloyd is a Master’s of Environmental Management (MEM ’13) candidate at the Yale School of Forestry and Environmental Studies. She is also a member of the Research Team for the 2012 Environmental Performance Index.