From the Harvard Business Review
The Dynamics of Personal Influence - by Nicholas A. Christakis
You may have noticed how fashions in clothes or music spread through social networks. It turns out that all kinds of conditions and behaviors – including obesity, smoking, altruism, voting and happiness - can flow through them as well. Yet although a person may be connected to other people by six degrees of separation, he or she is influenced only by those up to three degrees away. My colleague James Fowler and I have also found that a person’s influence progressively diminishes as the degrees of separation increase. For example, the risk for smoking in a person connected to a smoker (that is, at one degree of separation) is 61% higher, on average, than would be expected as a result of chance. It is 29% higher if the friends of that person’s friends smoke, and 11% higher if the friends of the person’s friends’ friends smoke. By the fourth degree of separation there is no longer an increase in risk. To take another example,we have found that a person is 15% likelier to be happy if his or her friends are happy, 10% likelier if the friends’ friends are happy, and 6% likelier if the friends of those friends’ friends are happy.
What does all this mean for businesses? Pharmaceutical companies might target physicians more efficiently by exploiting their tendency to be influenced by other physicians to whom they are connected. Workplace-safety initiatives might benefit from the understanding that one person who adopts safer practices influences others to do so. Efforts to foster creativity or innovation might depend on the degree of separation of the relevant parties. And groups of customers – including customers who have online connections – might be strategically targeted so as to take advantage of their influence on one another.
Nicholas A. Christakis is a physician and a professor of sociology at Harvard University in Cambridge, Massachusetts.