The Impossibility of Measuring Greenness

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If you have been following me for a while, you know that I am a skeptic about the ability of life-cycle analyses and all related indices or ratings based on them to allow consumers to make meaningful decisions about the products they choose to purchase. My resistance comes from two sources. The first has to do with the methodologies, and the second with the basic idea that numbers and the analyses that produce them can describe reality sufficiently to ground purely rational processes.

All composite measures of environmental and social impacts are just that--a melange of factors spanning all the environmental media in the first case, and a similar set trying to capture what makes life good for humans. The aggregation of multiple impacts into a single quantity (numerical index/score) categories requires the imposition of values applied to each of the factors involved. Kenneth Arrow won a Nobel Prize in Economics largely on the recognition of the importance of his "impossibility theorem." Arrow argues that it is impossible to combine three or more independent preferences into a single stable ranking. Although Arrow originally was writing about voting outcomes, the concept applies to any situation where preferences are used to determine the outcome. The weights applied to the importance of the individual factors in impacts metrics are inherently just preferences.

The UN's Human Development Index weighs the three factors--GDP, life expectancy or education--equally although there is great disagreement over the relative importance of the factors. Indices, like those presented in GoodGuide or the proposed Walmart Sustainability Index, aggregate tens to hundreds of single factors. The weights are determined by consensus of experts, but that does not mean they conform to consumers preferences. Now add other preferences that consumers carry into the store, and it's easy to see that there is little correlation between the indices and outcomes in the world.

The second reason springs from the general belief that we can model reality with analysis. Modern science has allowed us to do that, but only for very limited contexts. But the context that sustainability indices and social indicators pertain to is the messy world. Years ago the philosopher Alfred North Whitehead gave us the wonderful phrase, "The fallacy of misplaced concreteness." Whitehead was telling us that we have become enchanted by the idea of analysis and forget that models are only models. The mere presentation of an index, especially when measured to two significant figures suggesting great precision, is taken as real in the sense that "rational" decisions can be based on the numbers.

All this technical stuff here was inspired by reading an recent article in the Guardian. George Monbiot, a well-known British environmental journalist, recanted his former position that veganism was always greener that meat eating. Exactly how he came to that decision was not elaborated, but it seems clear it was on the basis of some life-cycle analysis. Monbiot was now saying the preferred diet is not so clear. It all depends . . . I am pretty sure the outcome rests on the choice of factors (one kind of preference) and their weights (another kind of preference). Monbiot's admission was important in getting a better understanding of the practical limitations of composite indices out into the general public.

There surely are methods that can help us make environmental and social choices. Even with my reservations above, these methods can usually show the difference between very bad choices and very good choices, but the great middle area is often the one where we live. The purported precision and even the indices, per se, convey to the consumer that he or she is doing their part for sustainability or social justice by choosing the higher scoring product or action. In reality, the Earth system depends on the absolute levels of harm inflicted. A somewhat greener purchase still adds to the total burden. Even though we should always try to make the better choice, we are still, to use a metaphor I invoked a couple of blogs ago, rearranging chairs on the Titanic.

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1 Comments

Ricardo Sans said:

Sr. Ehrenfeld

Gracias al libro de Daniel Goleman, Inteligencia Ecologica, llego a sus ideas las cuales leo y analizo con mucho interes.

Lo felicito por su labor, que espero pueda continuar por muchisimos aƱos mas.

Reciba una estimulo desde Venezuela.

Le saluda y aprecia, Ricardo Sans