Publication Bias in the Returns to R&D Literature

The returns to R&D literature is large and has been surveyed on several occasions. We complement previous surveys by discussing the scope for publication bias and illustrate how formal meta analytic techniques can be used to analyse the problem. We find evidence consistent with positive publication bias and discuss possible interpretations. The bias appears to be particularly strong in the part of the literature that controls for unobserved firm fixed effects. The reason may be that fixed effects specifications are particularly susceptible to measurement errors and therefore have a high probability of producing implausibly low return estimates. Implausible estimates are likely to be filtered out before being reported, and our analysis suggests that 23 % of a hypothetical complete literature is missing. Future reviews should take into account that the full effect of negative specifications biases may be masked by reporting and publication bias.