This paper builds on previous research on changes in the historical behavior of the cyclical relationships
captured in Okun’s original 1962 “law.” While I have been doing research since 1993 within the framework
of the “output identity” used here, this paper has benefitted from Bob Hall’s flagging the existence
of a BLS series on aggregate labor hours based on the household survey. Thanks also to Bob Hall
for providing the detailed data on structural changes in the labor-force participations rate that are an
input into his latest paper (2014). I am grateful to John Fernald for our many exchanges on the substance
and exposition of this paper and the reasons for the differences between my results and his (see Fernald,
2014). Dan Sichel contributed an extensive mark-up of the paper and I have faithfully adjusted it in
response to his many constructive suggestions. This paper would not have been possible without the
inspired research assistance of Leo Zhu, who performed the calculations within minutes, not hours,
and who read my mind in creating elegantly formatted graphs almost before I thought them up. The
views expressed herein are those of the author and do not necessarily reflect the views of the National
Bureau of Economic Research