My estimates are qualitatively similar to Del Negro et al. (2015), who also find a negative natural rate and a
gradual normalization to long-run levels. Williams (2015) estimates the natural rate to be low by historical
standards, but not nearly as low as those shown in Figure 1. The main difference is that Williams uses the
statistical model of Laubach and Williams (2003), which is better suited to determine the longer-run level
of the natural rate. By contrast, my analysis is suited to find short-term fluctuations in the natural rate.