After studying 25 statistical series, of
which ten concerned the French economy, eight the British, four the US, one (coal)
the German and two (pig iron and coal production) the world economy as a whole, he
identified the three cycles with the initial upswings starting in 1790, 1844 and 1895.
The peak-to-trough length of the cycles was 20–30 years, with an overall trough-
to-trough length of approximately 50 years.