اقتصاد کشاورزی و توسعه

اقتصاد کشاورزی و توسعه

قابلیت اطمینان و اعتبار در مطالعات ارزش‌‏گذاری مشروط: مبانی نظری و آزمون‏‌ها

مقالات آماده انتشار

نوع مقاله : مقاله پژوهشی

نویسندگان
فرشاد محمدیان 1
احمد سام دلیری 2
1 استادیار گروه اقتصاد کشاورزی، دانشکدة کشاورزی، دانشگاه سیدجمال‌الدین اسدآبادی، اسدآباد، ایران.
2 استادیار گروه اقتصاد کشاورزی، دانشکده کشاورزی، دانشگاه سید جمال‌الدین اسدآبادی. اسد آباد. ایران.
10.30490/aead.2026.367525.1694
چکیده
با وجود کاربرد گستردة «مطالعات ارزش‌‏گذاری مشروط»، همواره این‏گونه پژوهش‌‏ها با انتقادات جدی در خصوص قابلیت اطمینان و اعتبار نتایج آن مواجه بوده‌ و در عمل، ماهیت فرضی بودن سناریوها، اتکا به پاسخ‌‏های اظهارشده و عدم وجود رفتار واقعی بازار به بروز انواع مختلف تورش‏‌ها در فرآیند طراحی، اجرا و تحلیل این مطالعات انجامیده است. از این‌‏رو، صرف استفاده از روش ارزش‌‏گذاری مشروط و بدون ارزیابی دقیق کیفیت داده‌ها از دید بسیاری از پژوهشگران و داوران علمی قابل قبول نیست. در واکنش به این چالش‌ها، ارزیابی قابلیت اطمینان و اعتبار مطالعات ارزش‌‏گذاری مشروط بیش از پیش در کانون توجه قرار گرفته و با وجود تأکید گسترده ادبیات بر اهمیت این مفاهیم، در بسیاری از مطالعات تجربی ارزش‌‏گذاری مشروط، آزمون‏‌های قابلیت اطمینان و اعتبار یا به‌صورت محدود انجام شده یا صرفاً به‌صورت توصیفی گزارش شده است. بر این اساس، مطالعه حاضر با هدف شناسایی و تبیین انواع تورش‌‏ها در مطالعات ارزش‏‌گذاری مشروط و بررسی آزمون‏‌های قابلیت اطمینان و اعتبار انجام شد. به ‏منظور ارائه نمونه‌ای عملی، انواع آزمون اعتبار در مطالعه سام‏‌دلیری (Samdeliri, 2023) در زمینة محاسبه ارزش‌‏های تفرجی دریاچه آویدر شهرستان نوشهر که با روش ارزش‌‏گذاری مشروط (CVM) انجام شده بود، مورد بررسی قرار گرفت. نتایج نشان داد که اعتبار محتوایی، اعتبار ساختاری و اعتبار بر مبنای انتظارات مطالعه بالا و اعتبار همگرایی آن تا حدودی پایین بوده است.
کلیدواژه‌ها
ارزش&rlm
‌گذاری مشروط، هزینة سفر، تورش، قابلیت اطمینان، اعتبار.

موضوعات

عنوان مقاله English

Reliability and Validity in Contingent Valuation Studies: Theoretical Bases and Tests

نویسندگان English

Farshad Mohammadian 1
Ahmad Samdeliri 2
1 Assistant Professor, Department of Agricultural Economics, Sayyed Jamaleddin Asadabadi University, Asadabad, Iran.
2 Assistant Professor, Agricultural Economics, Sayyed Jamaleddin Asadabadi University, Asadabad, Iran.
چکیده English

Introduction: The Contingent Valuation Method (CVM) is one of the most widely used tools for estimating non-market environmental values in natural resource and environmental economics. Despite its extensive application in policy analysis, concerns regarding the reliability and validity of CVM estimates remain a central issue in the literature. A substantial number of empirical studies either implement these tests in a limited manner or report them only descriptively. Such methodological shortcomings may lead to the use of unreliable estimates in environmental management and policy-making. This study aimed at clarifying the theoretical foundations of reliability and validity in CVM studies and providing an applied framework for their evaluation. Therefore, the main contribution of this study lies in integrating theoretical discussion with empirical evidence and demonstrating the practical assessment of validity tests using data from a previous CVM study (Samdeliri, 2023) on the recreational value of Avidar Lake in Nowshahr County, Iran. The results were expected to contribute to improving the design, implementation, and interpretation of CVM studies in environmental economics. 
Materials, Methods and Theoretical Framework: In non-market valuation studies, reliability refers to the stability and reproducibility of valuation results, indicating whether a measurement instrument yields consistent outcomes under similar conditions. Validity, in contrast, addresses whether CVM estimates truly reflect individuals’ economic preferences for the proposed environmental change rather than hypothetical responses, general attitudes, or strategic behavior. The distinction between these two concepts is particularly important in CVM, as a study may exhibit high reliability while lacking sufficient validity. Accordingly, reliability is a necessary but not sufficient condition for validity. Reliability in CVM studies encompasses several dimensions, including test-retest reliability, internal reliability, inter-interviewer reliability, and equivalent-form reliability. These dimensions are commonly assessed using correlation coefficients between Willingness-to-Pay (WTP) estimates obtained at different points in time, Cronbach’s alpha for attitudinal or awareness scales, intraclass correlation coefficients for repeated samples, and mean comparison tests to examine the absence of statistically significant differences across survey rounds or questionnaire versions. Validity in CVM is inherently multidimensional and includes content validity, construct validity, convergent validity, discriminant validity, criterion validity, and validity based on theoretical expectations. Content validity examines whether the valuation scenario is understandable and credible, whether the payment vehicle is realistic, and whether all relevant components of environmental value are adequately covered. This type of validity is typically evaluated through expert judgment and pilot testing. Construct validity assesses whether estimated WTP behaves in accordance with economic theory, often by examining its relationship with key socioeconomic variables such as income, education, and environmental awareness. Convergent and discriminant validity are evaluated by comparing CVM estimates with results obtained from alternative valuation methods or with variables that are theoretically related or unrelated to WTP. Validity based on theoretical expectations focuses on whether CVM estimates are consistent with prior empirical evidence and established economic intuition. In this study, content validity of the previous CVM survey (Samdeliri, 2023) was assessed through expert review. Construct validity was examined using a regression framework in which WTP is specified as a function of income, education, and an environmental awareness index. Convergent validity and validity based on expectations were evaluated by comparing CVM results with estimates derived from using Travel Cost Method (TCM). 
Results and Discussion: The qualitative assessment of the questionnaire by environmental and natural resource experts indicated that the valuation scenario, payment vehicle, and questionnaire structure were clear, coherent, and conceptually sound, and that they adequately captured the relevant dimensions of environmental value. These findings support the content validity of the CVM study. Regression results showed that income, education, and environmental awareness had statistically positive effects on WTP. These results are consistent with theoretical predictions in environmental economics and therefore, support the construct validity of the CVM estimates. To assess convergent validity, recreational values estimated using CVM were compared with those obtained from TCM. The CVM results indicated that the average individual WTP in 2019 was 104,660 IRI rials, which after adjusting for a 40 percent inflation rate in 2020, corresponded to approximately 146,520 IRI rials per recreational visit. In contrast, TCM estimates for 2020 suggested a shadow price of approximately 449,280 IRI percent per visit. These findings imply that CVM estimates amount to roughly one-third of TCM estimates, indicating relatively low convergent validity. However, from the perspective of validity based on theoretical expectations, these results are defensible. The TCM reflects actual revealed behavior, whereas CVM relies on a hypothetical market and may be affected by hypothetical bias and the public good nature of environmental resources. Therefore, higher estimates obtained from TCM relative to CVM are consistent with economic intuition and prior empirical findings.
Conclusion and Suggestions: This study highlighted the importance of systematically assessing both reliability and validity in CVM studies to enhance the credibility of non-market valuation results. While the examined study demonstrates acceptable content validity, construct validity, and validity based on theoretical expectations, its convergent validity is limited. These findings underscore the need for caution when interpreting CVM estimates in isolation. Future research is encouraged to compare CVM results not only with the TCM but also with other non-market valuation approaches, particularly simulated market methods, to provide more robust evidence regarding the validity of estimated environmental values.

کلیدواژه‌ها English

Contingent Valuation
Travel Cost
Bias
Reliability
Validity
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اقتصاد کشاورزی و توسعه

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