Perturbation, networks and business cycles: Bernard Chait's pioneering work in econometrics*

The little-known Belgian engineer Bernard Chait contributed to business cycle theory by means of a mathematical model, of which the 'law of divergence' was an important building block. The law of divergence has been interpreted as a generalization of the acceleration principle. This paper draws upon published and archival sources to examine the sources of Chait's thinking, explain the basics of his model and assess the impact of his work. His relations with Francois Divisia and Jan Tinbergen are explored and his claim that Leontief's dynamic input - model was an unacknowledged reformulation of his own work is analysed.