If my memory is correct, the Dutch amateur economist Sam de Wolff discovered the long wave at the same time as Kondratieff. SdW did not publish his findings in a professional journal and was not credited ("named") for his work (although Schumpeter apparently did mention him in this context), most of which was reported in Dutch and/or German. SdW ascribed cyclicity to solar activity -- which is interesting because his own work in capital theory should have led him to a better explanation. Based on his rather peculiar statistical decompositions, he predicted the timing of the collapse of 1929 and that of the subsequent turning point. History of Thought is not my field -- the above is written from memory only. Apologies for any errors. Jesse Vorst