基于CVM的耕地保护外部性估算与检验

Calculating and testing cultivated land protection externality using Contingent Valuation Method

为了科学评估耕地保护的外部性,在耕地利用效益体系重构和耕地保护外部性界定的基础上,基于条件价值评估法(CVM)构建了耕地保护外部性测度、分析和检验一体化的方法体系,并以河南省焦作市为研究区域进行了实证应用。研究结果表明:1耕地生态社会效益属于一种纯粹的、具有正外部性和私人(主要为农户)联合提供的混合类跨区域性公共物品,可以运用CVM等非市场价值评估法进行估算。2受访者的支付意愿较大程度地受社会经济发展水平的制约和影响,农户和城镇居民对耕地生态社会效益认知度的高低是造成城镇居民与农户支付率差异的重要影响因素。3基于CVM测算出的焦作市耕地整体外部性为1.91亿元·a-1,耕地保护外部性为993.7元·hm-2·a-1,该测算结果可作为耕地保护外部性补偿的最低标准。4CVM的有效性与可靠性检验是CVM理论、方法和实践内容的重要组成部分,可通过问卷设计优化、预调查、问卷内容修正、合理的询价方式、不同估算方法的对照分析、同一方法重复试验等手段进行有效性与可靠性检验;检验结果表明,CVM进行耕地保护外部性估算的可靠性和有效性较高。

This paper proposed the Contingent Valuation Method（CVM） for estimating cultivated land protection externality. The proposed CVM was based on reconstruction of cultivated land utilization benefit system and defined cultivated land protection externality. The paper discussed in detail specific techniques of sample size and distribution, determination of leading technology,pay/compensation interval setting, hypothetical market scenario setting, evasion of deviation, pretreatment of survey data, and results validity/reliability tests. The results showed that ecological and social benefits of cultivated lands included public goods with mixed classes across categories. These classes were provided by joint ventures between the pure positive externalities and the private sector（mainly farmers）. This could be estimated by using CVM and other non-market valuation methods. The willingness to pay of interviewee for this service was heavily restricted and influenced by their levels of socioeconomic development. The recognition of ecological and social benefits of cultivated lands of farmers and urban residents formed the main causality factor for the differences in payment ratio between urban residents and rural farmers. Urban residents were more familiar with ecological and social benefits of cultivated lands than rural/farm households. This was probably a key factor influencing the willingness to pay for ecological services.Farm households preferred voluntary labor as mean of payment, while both money and voluntary labor were more preferred by urban residents. The probable reason for this was that farm households had more leisure time than urban residents. Unitary cultivated land protection externality for Jiaozuo City was 1.91×10^8 Yuan·a^-1 and the cultivated land protection externality per unit area of cultivatedland was 993.7 Yuan·hm^-2·a^-1 base on CVM. CVM validity and reliability test was a critical element of CVM theory, method and practice. This was obtained through questionnaire optimization, pre-survey, questionnaire revision, rational inquiry, comparative analysis of different estimation methods, and repeated tests of the same method. The test results showed it was reliable and valid to use CVM estimating the cultivated land protection externality.