Cautionary tales of fat tails

Distributions of GDP fluctuations that exhibit fat tails shed doubt on the suitability of Normal distributions in empirical and theoretical business-cycle analyses. We document: (i) fat tails in US output fluctuations are not a pervading characteristic of the entire post-war sample, and appear in subsamples exhibiting declines in cyclical and trend volatility (e.g., the Great Moderation); (ii) a DSGE environment featuring Normal shocks that match the declines in observed cyclical and trend volatility can explain almost all of the fat-tailed characteristics observed in the data, leaving little support for the role of rare, large shocks delivering fat-tailed distributions.