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The dispersion and development of consumer preferences for genetically modified food — A meta-analysis

The introduction of genetically modified (GM) content in food products has been the object of highly controversial debates in several countries for over a decade. Opponents, such as Greenpeace International, warn against potential risks to the environment and human health that arise from growing and consuming GM crop (Greenpeace International, 2008). They emphasise possible but not yet identified health risks, allergic reactions, and environmental risks, such as pest resistance and loss of biodiversity, and denounce the absence of long-term studies investigating these risks. On the other hand, proponents, such as the Council for Biotechnology Information, believe that the approval process in place for the commercialisation of GM foods is sound and that GM crops can have positive environmental impacts due to reduced pesticide and herbicide use, positive social impacts due to an increase in farmland productivity and positive health impacts, since they reduce farmers' exposure to toxic substances, especially in developing countries (Council for Biotechnology Information, 2008).

Given the distribution of conflicting information and the resulting uncertainty among consumers, politicians face the pressing problem of how to regulate the GM food market. There are three main options (Noussair et al., 2008): (i) banning GM foods, (ii) allowing GM foods without segregation from their conventional counterparts and (iii) allowing GM foods with segregation from their conventional counterparts. The first two policies have serious potential drawbacks. Banning GM products may be inefficient since potential welfare gains from the use of biotechnology would thus not be realised. On the other hand, allowing the introduction of GM foods into the food chain without segregation reduces consumer choice and, given consumers' strong resistance, may cause the collapse of entire market segments. The third option implies the creation of two separate production tracks and the introduction of a labelling scheme allowing consumers to choose between GM and non-GM food products. While segregation and labelling of GM products are beyond dispute, the choice of the labelling scheme, mandatory or voluntary, is a highly controversial issue. Some countries, such as the United States and Canada, have opted for a voluntary labelling scheme arguing that the market will offer the appropriate labelling incentives and produce an optimal degree of segregation among products without the unnecessary costs a mandatory scheme would imply (Huffman et al., 2002). Other countries, such as the European Union member states, Australia, New Zealand and Japan have opted for a mandatory labelling scheme arguing that consumers have the right to know.

In order to elicit consumer preferences for GM food and help politicians to efficiently regulate the market, numerous GM food valuation studies have been conducted., These studies, however, present a wide range of valuation estimates and, due to differences with respect to elicitation procedures, sample characteristics, products, and regional focus, a direct comparison of results and an explanation of what determines the large study-to-study variation in valuation estimates becomes challenging. Against this background, the aim of this paper is to identify the determinants of the variation in GM food valuation studies. Furthermore, the dispersion of consumer preferences and their development over time will be analysed. For this purpose, a meta-analysis of 51 studies is conducted which report a total of 114 valuation estimates for GM food.

The paper is structured as follows. Section 2 gives a short review of the relevant literature. Section 3 describes the data derived from the primary studies. Section 4 presents the results of the meta-regression model. Section 5 analyses the robustness of the results and presents several sensitivity tests. Section 6 summarises the key findings and concludes.