The introduction of genetically modified (GM) content in food products has been the object of controversial debates in several countries for more than a decade. Opponents warn against potential dangers to the environment and human health which arise from growing and consuming GM crops. Proponents believe that the current approval process for the commercialisation of GM foods is sound and that GM crops can have positive environmental, health and social impacts. Given these conflicting lines of argumentation, politicians face the challenge of how to regulate the GM food market. Numerous GM food valuation studies have been conducted in order to elicit consumer preferences for GM food and help politicians to efficiently regulate the market. These studies, however, present a wide range of valuation estimates and, due to differences with respect to estimation procedures, sample characteristics, products, and regional focus, a direct comparison of results and an explanation of what determines study-to-study differences becomes challenging. Against this background, the aim of this paper is to identify the determinants of the variation in GM food valuation studies. For this purpose, a meta-analysis of 46 primary studies reporting a total of 108 valuation estimates for GM food is conducted. Given the large variety of estimation procedures across studies, meta-analysis is a good opportunity to test for methodological differences. The results show that elicitation methods and formats used in the primary studies affect valuation estimates to a much larger extent than do sample characteristics. Moreover, consumer aversion to GM food seems to have increased over time. Previous findings that consumer valuation strongly depends on the type of food product and varies among regions are confirmed.
Dannenberg, Astrid (2008), Is it Who You Ask or How You Ask? Findings of a Meta-Analysis on Genetically Modified Food Valuation Studies, ZEW Discussion Paper No. 08-096, Mannheim.