Figure 2 shows the correlation between principals and contacts with regards to their drinking behavior (numerical results for this and the other figures can be found in the online appendix). The results indicate that principals are 50% (95% C.I. 40% to 62%) more likely to drink heavily if a person they are directly connected to (at one degree of separation) drinks heavily. The size of the effect for people at two degrees of separation (e.g., the friend of a friend) is 36% (95% C.I. 25% to 48%) and for people at three degrees of separation (e.g., the friend of a friend of a friend) is 15% (95% C.I. 8% to 25%). At four degrees of separation, the effect disappears (4%, 95% C.I. –2% to 10%), in keeping with the “three degrees of influence” rule of social network contagion that has been exhibited for obesity, smoking, happiness, depression, loneliness, word-of-mouth advertising, and the spread of ideas among inventors (10-14,31). Analyses of the full network also show that subjects are 29% (95% C.I. 23% to 36%) more likely to abstain if a
