The Penn World Tables (PWT) are an important data source for cross-country comparisons in economics. The PWT have undergone several revisions over time. This paper documents how countries' output growth rates change across four publicly available versions of the PWT. We show that for some countries the magnitude of the differences is significant and/or the sign of the growth rates changes across versions. Using as an example .Ramey and Ramey (1995), who found growth volatility has a significant negative effect on growth, we demonstrate that conclusions based on one version of the PWT may not hold under another version.