"~80% of the 50 largest public companies are connected to one another through 1 or more shared board member(s)" [1]
The "three most connected companies" through interconnecting directors are "3M (7 connections), Boeing (6 connections) and Amgen (6 connections)" ... "Other highly-connected companies include Walt Disney, Apple, Chevron, Exxon Mobil, IBM, and Procter & Gamble – each has five board members that also serve for other top 50 corporations." [2]