existence of a perfectly competitive labor market for a wage-risk hedonic study. In addition, these studies often have to ignore the potentially important roles played by age and health status in mortality risk reduction valuation (Krupnick et al. 2002; Arberini et al. 2004 and Hammitt and Liu, 2005). Given the fact that people living in different countries do not necessarily share the same demographical structures and health characteristics, the simple scaling principle or the independent-variable-based scaling principle do not permit us to include the differences existing in the original mortality risk between the countries. Chestnut et al. (1997), based on two paralleled CV studies in Bangkok and Los Angeles, revealed that the differences in the average increase in the incidence rate for certain respiratory diseases with the same percentage increase of pollution are incomparable between the two cities.

Obviously if it is feasible, it is always preferable to conduct VSL studies directly for a country itself. A small number of contingent valuation studies have been designed and carried out in developing countries to estimate VSL. Alberini et al. (1997), Alberini and Krupnick (2000), Hammit and Graham (1999), Hammit and Liu (2004), and Bhattacharya et al (2007) are a few examples. Only until very recently a couple of contingent valuation studies have been conducted in China to estimate VSL. Wang and Mullahy (2006) conducted a CV study in Chongqing to estimate WTP for reducing the risk of fatality due to air pollution and the value of a Chinese statistical life. Based on the face-to-face interviews of 550 individuals in 1998 with an open-end WTP question format backed by a bidding game in case of respondent’s hesitation, a probit estimation and bootstrap process gives an estimate of medial WTP for saving a statistical life to be 286,000 yuan, or 34,458 US dollars. Hammitt and Zhou (2006) estimated WTP values for three health endpoints: cold, chronic bronchitis and fatality, based on an in-person interview conducted in 1999. The survey was carried out in three locations: Beijing, Anqing and the rural areas near Anqing. WTP was elicited by a double-bounded, dichotomous-choice format. Each respondent was asked whether she/he would purchase a treatment which provides a stated risk reduction at a specified price. After the two dichotomous-choice questions, the respondents were asked to state their maximum WTP for the risk reduction in an open-ended follow-up. Their estimations gave a sample-average median value of a statistical life ranging between 33080 yuan to 140590 yuan ($4000 to $17,000). Both studies only concentrate their surveys in a geographically limited regions, therefore the conclusion cannot be simply extrapolated to other regions, given the great regional disparities between different provinces. Both surveys related their mortality reduction WTP questions directly to environmental quality improvements. Although the studies reminded respondents to only evaluate their mortality risk reduction contributed by environmental quality improvements, the respondents might not have totally excluded from their valuation other benefits caused by pollution reduction. The vast differences in the estimation results call for further investigations.

# **4.   Contingent Valuation of a Statistical Life**

The linkage between a WTP for fatal risk reduction and VSL can be constructed from a lifecycle consumption model with an uncertain lifetime (Yaari, 1965; Sherpard and Zeckhauser, 1982; Cropper and Sussman, 1990). Following Alberini et al. (2004), the life-cycle model can be summarized below.

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