Quantitative Laws of Propagation

Tarde was not content to describe the mechanisms of social life. He wanted to measure them. The aspiration was unusual for a sociologist of his era — most contemporaries treated quantification as the province of the natural sciences — but Tarde's magistrate background had given him an empirical disposition that resisted the purely theoretical. He had observed the actual pathways by which criminal techniques spread between offenders, the actual speed at which rumors propagated through small communities, the actual patterns by which fashions moved from Parisian salons to provincial drawing rooms. The patterns had regularities. The first regularity was geometric progression — successful imitations spread not linearly but exponentially, producing the S-curves that Everett Rogers would formalize seven decades later. The second was preferential flow from prestigious to aspirational positions. The third was the predictable interaction between novel and established imitative patterns, governed by relative prestige, content compatibility, and network density.