it deserved. Clement Juglar (1819—1905), the French physician turned economist, was the
first to make systematic use of time-series data to study business cycles, and is credited
with the discovery of an investment cycle of about 7—11 years duration, commonly known
as the Juglar cycle. Other economists such as Kitchin, Kuznets and Kondratieff followed
Juglar’s lead and discovered the inventory cycle (3—5 years duration), the building cycle
(15—25 years duration) and the long wave (45—60 years duration), respectively. The
emphasis of this early research was on the morphology of cycles and the identification
of periodicities. Little attention was paid to the quantification of the relationships that
may have underlain the cycles. Indeed, economists working in the National Bureau of
Economic Research under the direction of Wesley Mitchell regarded each business cycle
as a unique phenomenon and were therefore reluctant to use statistical methods except in
a non-parametric manner and for purely descriptive purposes (see, for example, Mitchell,
1928 and Burns and Mitchell, 1947). This view of business cycle research stood in sharp
contrast to the econometric approach of Frisch and Tinbergen and culminated in the famous
methodological interchange between Tjalling Koopmans and Rutledge Vining about
the roles of theory and measurement in applied economics in general and business cycle
research in particular. (This interchange appeared in the August 1947 and May 1949
issues of The Review of Economics and Statistics.)