Are Crop Yields Normally Distributed?

The evidence for nonnormality of crop yields is reassessed. Three methodological problems are identified in typical yield distribution analyses: (i) misspecification of the nonrandom components of yield distributions, (ii) missreporting of statistical significance, and (iii) use of aggregate timeseries (ATS) data to represent farm-level yield distributions. One or more of these problems infect virtually all evidence against normality to date. The positive contribution of the article is a set of principles that must be followed in any valid investigation of yield normality. Copyright 1999, Oxford University Press.