  The increasing policy interests and the vivid academic debate on non-tariff
measures (NTMs) has stimulated a growing literature on how NTMs affect agrifood
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.
