Milligan Craig, Kopp Andreas, Dahdah Said, Montufar Jeannette
World Bank, Washington DC.
World Bank, Washington DC.
Accid Anal Prev. 2014 Oct;71:236-47. doi: 10.1016/j.aap.2014.05.026. Epub 2014 Jun 19.
We model a value of statistical life (VSL) transfer function for application to road-safety engineering in developing countries through an income-disaggregated meta-analysis of scope-sensitive stated preference VSL data. The income-disaggregated meta-analysis treats developing country and high-income country data separately. Previous transfer functions are based on aggregated datasets that are composed largely of data from high-income countries. Recent evidence, particularly with respect to the income elasticity of VSL, suggests that the aggregate approach is deficient because it does not account for a possible change in income elasticity across income levels. Our dataset (a minor update of the OECD database published in 2012) includes 123 scope-sensitive VSL estimates from developing countries and 185 scope-sensitive estimates from high-income countries. The transfer function for developing countries gives VSL=1.3732E-4×(GDP per capita)(∧)2.478, with VSL and GDP per capita expressed in 2005 international dollars (an international dollar being a notional currency with the same purchasing power as the U.S. dollar). The function can be applied for low- and middle-income countries with GDPs per capita above $1268 (with a data gap for very low-income countries), whereas it is not useful above a GDP per capita of about $20,000. The corresponding function built using high-income country data is VSL=8.2474E+3×(GDP per capita)(∧).6932; it is valid for high-income countries but over-estimates VSL for low- and middle-income countries. The research finds two principal significant differences between the transfer functions modeled using developing-country and high-income-country data, supporting the disaggregated approach. The first of these differences relates to between-country VSL income elasticity, which is 2.478 for the developing country function and .693 for the high-income function; the difference is significant at p<0.001. This difference was recently postulated but not analyzed by other researchers. The second difference is that the traffic-risk context affects VSL negatively in developing countries and positively in high-income countries. The research quantifies uncertainty in the transfer function using parameters of the non-absolute distribution of relative transfer errors. The low- and middle-income function is unbiased, with a median relative transfer error of -.05 (95% CI: -.15 to .03), a 25th percentile error of -.22 (95% CI: -.29 to -.19), and a 75th percentile error of .20 (95% CI: .14 to .30). The quantified uncertainty characteristics support evidence-based approaches to sensitivity analysis and probabilistic risk analysis of economic performance measures for road-safety investments.
我们通过对范围敏感的陈述偏好统计生命价值(VSL)数据进行按收入分类的元分析,构建了一个用于发展中国家道路安全工程的VSL转移函数模型。按收入分类的元分析分别处理发展中国家和高收入国家的数据。以前的转移函数基于主要由高收入国家数据组成的汇总数据集。最近的证据,特别是关于VSL的收入弹性,表明汇总方法存在缺陷,因为它没有考虑到不同收入水平下收入弹性可能的变化。我们的数据集(2012年发布的经合组织数据库的小幅更新)包括来自发展中国家的123个范围敏感的VSL估计值和来自高收入国家的185个范围敏感的估计值。发展中国家的转移函数为VSL = 1.3732E - 4×(人均国内生产总值)^2.478,其中VSL和人均国内生产总值以2005年国际美元表示(国际美元是一种与美元具有相同购买力的名义货币)。该函数可应用于人均国内生产总值高于1268美元的低收入和中等收入国家(非常低收入国家存在数据缺口),而在人均国内生产总值约20,000美元以上则不适用。使用高收入国家数据构建的相应函数为VSL = 8.2474E + 3×(人均国内生产总值)^0.6932;它对高收入国家有效,但对低收入和中等收入国家的VSL估计过高。该研究发现,使用发展中国家和高收入国家数据建模的转移函数之间存在两个主要显著差异,支持分类方法。这些差异中的第一个与国家间VSL收入弹性有关,发展中国家函数的弹性为2.478,高收入国家函数的弹性为0.693;在p < 0.001时,差异显著。这一差异最近由其他研究人员提出但未进行分析。第二个差异是,交通风险背景在发展中国家对VSL有负面影响,而在高收入国家有正面影响。该研究使用相对转移误差的非绝对分布参数来量化转移函数中的不确定性。低收入和中等收入函数是无偏的,中位数相对转移误差为 - 0.05(95%置信区间: - 0.15至0.03),第25百分位数误差为 - 0.22(95%置信区间: - 0.29至 - 0.19),第75百分位数误差为0.20(95%置信区间:0.14至0.30)。量化的不确定性特征支持基于证据的方法,用于道路安全投资经济绩效指标的敏感性分析和概率风险分析。