Network Science Meets Al Capone

The Prohibition era, from 1920 to 1933, is remembered as a time when organized crime flourished in the U.S., and no name is more notorious than Al Capone in Chicago. But Capone’s organization didn’t operate in a vacuum: he had clients, suppliers, associates and acquaintances both legitimate and not so much, forming a vast network throughout the city.

Now two sociologists, Chris Smith, assistant professor of sociology at UC Davis and Andrew Papachristos, associate professor at Yale University, have brought modern network theory to the Roaring Twenties, compiling a database of the relationships in Prohibition-era Chicago and mapping out the links that held together Capone’s criminal empire. The work was published in June 2016 in the American Sociological Review.

The researchers dug through some 5,000 pages of documents from sources including the IRS, FBI, Chicago Crime Commission and the Chicago Tribune newspaper to compile their database. Then they used it to construct a network map plotting all the connections between about 3,000 different players in Capone’s network.

The network includes criminal associates as well as legitimate business owners, police and government officials, and ties through business (legal or not), friendships and family. Of particular interest are what the researchers call “multiplex” relationships, where two people were connected by more than one type of relationship — for example, through both business and family.

“Multiplexity was rare but relevant,” said Smith, in a Yale news release. “It was incredibly important for generating organized crime. Although only 10% of the relationships between organized crime individuals contained multiplex ties, these overlapping relationships integrated the criminal, legitimate, and personal networks and were essential to the operation of organized crime.”

— Andy Fell, UC Davis News and Media Relations