Mafia families were not exported to America but emerged spontaneously, as it were, when the supply of and the demand for protection met: when, in other words, a sufficient number of emigrants moved there for independent reasons, some bringing along the necessary skills for organizing a protection market, and when certain events, notably the Great Depression and Prohibition, opened up a vast and lucrative market for this commodity.

Diego Gambetta, The Sicilian Mafia The Busi…, loc. 665