This article aims to better understand the factors driving fluctuations in potential output measured by the production function approach (PFA.) To do so, the authors integrate a production function definition of potential output into a large-scale dynamic stochastic general equilibrium (DSGE) model in a fully consistent manner and give two estimated versions based on U.S. and euro-area data. The main contribution of this article is to provide a quantitative and comparative assessment of two approaches to potential output measurement, namely DSGE and PFA, in an integrated framework. The authors find that medium-term fluctuations in potential output measured by the PFA are likely to result from a large variety of shocks, real or nominal. These results suggest that international comparisons of potential growth using the PFA could lead to overstating the role of structural factors in explaining cross-country differences in potential output, while neglecting the fact that different economies are exposed to different shocks over time.