The effects of non-tariff measures on agri-food trade: a review and meta-analysis of empirical evidence

The increasing policy interests and the vivid academic debate on non-tariff measures (NTMs) has stimulated a growing literature on how NTMs affect agri-food trade. The empirical literature provides contrasting and heterogeneous evidence, with some studies supporting the 'standards as catalysts' view, and others favouring the 'standards as barriers' explanation. To the extent that NTMs can influence trade, understanding the prevailing effect, and the motivations behind one effect or the other, is a pressing issue. We review a large body of empirical evidence on the effect of NTMs on agri-food trade and conduct a meta-analysis to disentangle potential determinants of heterogeneity in estimates. Our findings show the role played by the publication process and by study-specific assumptions. Some characteristics of the studies are correlated with positive significant estimates, others covary with negative significant estimates. Overall, we found that the effects of NTMs vary across types of NTMs, proxy for NTMs, and levels of details of studies. Not negligible is the influence of methodological issues and publication process