We just finished reading Esty and Cornelius' Environmental Performance Measurement: The Global Report 2001-2002, where the ESI was discussed. We also looked at the 2002 ESI online. We are finding that the methodology sections (both in the book and online) are insufficient to allow us to replicate the rankings. We are interested in seeing how the rankings change if we impune our own weighting schemes, but to do so requires that we understand how they were done in the first place. So, here are our questions: 1. How were the z-scores for each of the variables converted to a percentile? 2. How were the percentiles converted to the indicator? Was this a sum of all the percentiles, an average of the percentiles, or something different? 3. How were the indicators compiled to create the overall ESI? 4. Were missing values included in all the above computations or were values imputed in the above prior to the computation of z-scores?

A first basic clarification is that the Esty and Cornelius chapters rely on the 2001 ESI, and the 2002 ESI made some changes to the methodology. The answer below is with regard to the 2002 ESI. Annex two in our 2002 ESI report has more detail, including some steps you didn’t ask about that would be necessary to replicate our rankings. For example, we converted some variables to log scales, and we trimmed the tails of extreme distributions.

1. How were the z-scores for each of the variables converted to a percentile?

We didn’t convert the z-scores to percentiles but rather left them as z-scores.

2. How were the percentiles converted to the indicator? Was this a sum of all the percentiles, an average of the percentiles, or something different?

The indicators are just the averages of the variables’ z-scores.

3. How were the indicators compiled to create the overall ESI?

The ESI is calculated by first averaging the indicators scores, and then converting that number to a standard normal percentile.

4. Were missing values included in all the above computations or were values imputed in the above prior to the computation of z-scores?

We made imputations at the variable level, not the indicator level. This would be the hardest step to replicate because we used a probablistic imputation procedure whose outcomes are not deterministic.

Environmental Sustainability Index

  1. Could you please let me know if there is any link between the ESI and Corporate Triple Bottom Line (TBL) Reporting? Alternatively, would you regard the ESI as a proxy for national TBL reporting?
  2. Could you please tell me how and with what kind of weighting the ecological footprint has been factored into the 2002 ESI?
  3. How often will the ESI be updated?
  4. I am currently evaluating different indices of sustainable development and came across the 2002 ESI profile for Belgium (Annex 5, p. 93).Could you explain why air quality is above average when the emission of air pollutants ('reducing air pollution') is extremely high?
  5. I am looking for the ESI reports for 2003 and 2004.   Is the ESI available for these years?
  6. I have read with interest the Environmental Sustainability Index that has been developed at Columbia University. For my Masters Thesis I am looking at developing a framework for measuring sustainability. I am particularly interested in measuring differences at the regional/state level. Would you see the application of the Environmental Sustainability Index at the state level as effective? Would it need to modified or could it serve as a useful comparison for states to national achievements.
  7. I read the 2002 Environmental Sustainability Index (ESI) where Uruguay is on 6th place. Its component score ranks range from 19th to 35th. Are other countries much more variable so their high ranking components are counterbalanced by low ranking components? I want to know which variables where the most important to put Uruguay in such a good place in the world list?
  8. I would like to do a time series analysis to look at the change in environmental sustainability in specific countries, but I am unsure if the data for your 2001 and 2002 ESI is different, or whether the 2002 ESI is just the result of fine-tuning definitions and categories.
  9. In reviewing the latest statistics on environmental sustainability from your website, I noted that the Faroe Islands was not listed. Could you please advise me on the criteria regarding who is included in the 2002 ESI rankings.
  10. Is it possible to do a time series analysis on the ESIs?
  11. We just finished reading Esty and Cornelius' Environmental Performance Measurement: The Global Report 2001-2002, where the ESI was discussed. We also looked at the 2002 ESI online. We are finding that the methodology sections (both in the book and online) are insufficient to allow us to replicate the rankings. We are interested in seeing how the rankings change if we impune our own weighting schemes, but to do so requires that we understand how they were done in the first place. So, here are our questions: 1. How were the z-scores for each of the variables converted to a percentile? 2. How were the percentiles converted to the indicator? Was this a sum of all the percentiles, an average of the percentiles, or something different? 3. How were the indicators compiled to create the overall ESI? 4. Were missing values included in all the above computations or were values imputed in the above prior to the computation of z-scores?
  12. We would very much appreciate you informing us on how you base your calculations on the profitability on water, or possibly its quality.
  13. What do the numbers "mean?"  That is, if Uganda's value is 0.65, does that mean that on a scale of 1-4 (1 being the least ? ) that Uganda is very unlikely to be exposed to the 6 hazards you describe?
  14. What does the "z" score for a peer group mean?
  15. What does the Peer Group ESI mean?
  16. What is the most recent version of the ESI?
  17. What is the reason that an EPI was established as a complement to the ESI?
  18. What were the data sources used for the 2001 ESI?
  19. Where can I find more information about the ESI 2002 methodology?

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