(WTP) for improvements in air quality. Each study is considered an observation and it consists in establishing an statistical relationship between the values obtained from the WTP (dependent variable) and certain variables representing the site in question (socioeconomic variables, geographical variables), which according to the judgment of the researcher have an impact on the study. Once the variables that have an influence on the observed differences in the individual valuations are determined, this additional information can be used to enhance the quality of the data obtained. The value transfers alternative can be considered to be a valid short-term solution. However, when thinking in long-term, the convenience of performing studies becomes crucial. Many air qualityrelated phenomena have particular features. For example, the experience in United States and Europe suggests that in the majority of urban centers the formation of O3 can be decreased with a reduction of VOC emissions primarily and NOx. Studies done in the Metropolitan Zone of Mexico ([Molina and Molina 2002], chapter 5) suggest, however, that it is actually convenient to reduce NOx emissions. Disregarding this fact, could lead to an excessive assignation of resources destined to reduce VOC emissions, without achieving the wanted results in the Metropolitan Zone of Mexico. 1.5 Cases of application of economic valuation of the air quality In this section some examples of the use of benefit valuation in an air quality policy are shown in different contexts. The aim of this section is to illustrate the reach and usefulness of these valuation techniques before describing in greater detail the study cases that will be seen in the next chapter. First there is a description of the use of air quality valuation in social cost-benefit analysis in the European Union, USA and a few developing countries, and secondly various judicial criteria for damage valuations are depicted. 1.5.1 The E.U. case In 1991 the European Commission began Project ExternE (http://externe.jrc.es). Its objective was to measure, in a detailed form, the external costs (or externalities) associated with the different fuel cycles. The adopted methodology for the project is based in a focus of the damage function and
19 COPERT is an acronym for: “Computer Program to Calculate Emissions from Road Transport�, available from
http://reports.eea.eu.int/Technical_report_No_50/en IDB-RPD Report 2
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