Origen, progresos y definición de la poesía

In the literature, although there are different taxonomies for valuation methods, mostly, the economic valuation methods have been divided into two groups:

1) Revealed preference methods (indirect), and 2) Stated preference methods (direct).

Revealed preference methods rely on data regarding individuals' preferences for or against a marketed good, which has an environmental attribute related to it in some way. These techniques rely on either actual market, for example, the property market where property prices reflect the various attributes of the property, including environmental attributes. Revealed preferences techniques include:

1) hedonic price method, 2) travel cost method,

3) random utility modeling, and 4) averting behavior.

The type of data and the absence of direct enquiry into individual preferences for environmental goods restrict revealed preference methods to estimates of use value only (DTLR 2003).

On the other hand, stated preference methods can be applied to any context. These techniques are the only methods that can estimate values for non-use values of environmental resources. Non-use values have been shown to be a significant portion of total economic value in the context of many natural resources, especially where the resource concerned is unique or the impact is irreversible. There are two major variants of stated preference methods:

1) contingent valuation, and 2) choice modeling.

Both variants use similarly structured questionnaires but differ in the way they define the environmental resource of concern. Contingent valuation is concerned with the resource as a bundle of different attributes or characteristics, while choice modeling is mainly concerned with the individual attributes of the resource (DTLR 2003, Brookshire and Coursey 1987, Loureiro, et al. 2003, Moons 2003, Smith 1993).

2.5.1. Revealed Preference Methods

There are various revealed preference methods. However, the study focused on two major revealed preference methods which are travel cost and hedonic price methods

Travel Cost Method (TCM) has been used to estimate mostly the value of

recreational sites. The method was first proposed by Hotelling in 1947. To visit a site people have to bear various costs. These include travel costs (petrol, train tickets, etc.), the opportunity cost of time and, possibly, an entry fee. People’s travel costs differ and so does their opportunity cost of time. Thus, effectively, different individuals pay different prices for access to any given recreational site. Hardarson and Hardarson (2000) indicated that by observing how visit rates change in response to different prices one can estimate a demand schedule for the recreational services of a given site from which one can estimate the total surplus recreationers derive from these services.

The application of the TCM has some difficulties. Hardarson and Hardarson (2000) reviewed the restrictions of TCM. One problem is related to the allocation of travel costs. Some studies only estimate purchases of petrol. Other studies also include costs relating to the maintenance of vehicles, such as insurance and depreciation. Second, the appropriate measure for the opportunity cost of time is also a bid issue. Most people cannot pick their working hours flexibly and recreational activity is mostly

at the expense of other similar activity. This casts doubts over using wage rates as measures of the opportunity cost of time. Many studies use some fraction of wage rates. The fraction varies somewhat but is typically lower than 50% and often around 1/3. Another issue is if and then how one should make allowances for the fact that travelers differ (e.g., some visit only for a day, other stays for weeks). No clear consensus has emerged on how this issue or the other issues discussed above can be resolved. Researchers’ choices relating to these issues can have a huge impact on welfare estimates. Third, likewise, the choice of functional form has been shown to have a significant impact on consumer surplus estimates. As in the case of the hedonic price function, economic theory does not, a priori, help much with the choice of functional form although it may be of some help in choosing between different models once they have been estimated. Statistical measures of fit and prediction are among the tools available to discriminate between functional forms. Comparisons of TCM estimates from different studies or comparisons with estimates obtained by other valuation methods, such as contingent valuation, can be of value in this regard.

Another revealed preference method is Hedonic Price Method. Since Chapter 3 reviewed it specifically, it was not repeated in this part.

2.5.2. Stated Preference Methods

The best known and most commonly used stated preference method is the contingent valuation method (CVM). In order to estimate the existence or non-use value of an environmental resource one has to depart from the revealed preference methods. Instead one must employ so-called stated preference methods (Hardarson and Hardarson 2000, Smith 1996). The ability of CVM to measure economic value is, however, by no means unquestioned. CVM is highly controversial and some critics go as far as to suggest that it is completely useless (see Venkatachalam 2004, Carson et al. 2001, Diamond and Hausman 1994). On the other hand, Hardarson and Hardarson (2000) stated that a more prevalent opinion is that CVM can be of some use although great care needs to be applied in the study design and in the interpretation of results.

The CV method was originally proposed by Ciriacy-Wantrup (1947) who was of the opinion that the prevention of soil erosion generates some extra market benefits” that are public goods in nature, and therefore, one possible way of estimating these

benefits is to elicit the individuals’ willingness to pay for these benefits through a survey method (see Portney 1994, Hanemann 1994). However, Davis (1963) was the first to use the CV method empirically when he estimated the benefits of goose hunting through a survey among the goose-hunters. Venkatachalam (2004) indicated that this method gained popularity after the two major non-use values, namely, option and existence values, have been recognized as important components of the total economic values in environmental economics literature, especially during the 1960s. While the conventional revealed preference methods such as travel cost method are not capable of capturing these non-use values, the only method that is identified for estimating these values is the contingent valuation method. Hence, a considerable amount of studies on CVM -both theoretical and empirical- have emerged including a large number of studies criticizing the CV method.

Early studies of CVM used predominantly open-ended (OE) questions which ask respondents to state a WTP for an environmental benefit or a minimum compensation for an environmental resource loss. Recently, the OE format has been largely replaced with dichotomous choice (DC). Dichotomous choice studies present respondents with an amount and ask them to state if they are willing to pay this amount for the environmental gain under study (Hardarson and Hardarson 2000).

Venkatachalam (2004) reviewed CVM extensively in terms of the developments and issues on the theoretical, methodological and empirical aspects. In his review, the contingent valuation method (CVM) is defined as a simple, flexible non-market valuation method that is widely used in cost-benefit analysis and environmental impact assessment (see also Mitchell and Carson 1989, Cummings, et al. 1986). The other areas in economics where the CV method is increasingly being applied are health economics, transportation safety, and cultural economics. Its application in environmental economics includes estimation of non-use values, non-market use values or both of environmental resources. Venkatachalam (2004) pointed out that, in recent years, this method is commonly used in developing countries to elicit the individual’s preferences for the basic infrastructural projects such as water supply and sanitation (see also Whittington, 1998).

However, this method is subject to severe criticism. The criticism revolves mainly around two aspects, namely, the validity and the reliability of the results, and the effects of various biases and errors (Venkatachalam 2004, see also Hausman 1993, Bateman and Langford 1997). Carson et al. (2001) reviewed this method in terms of

controversies, and discussed key areas of the debate over CV and the validity of passive use value. They concluded that many of the alleged problems with CV can be resolved by careful study design and implementation. They also indicated that claims that empirical CV findings are theoretically inconsistent are not generally supported by the literature. The debate over CV, however, has clarified several key issues related to non- market valuation and can provide useful guidance both to CV practitioners and the users of CV results.