About a year ago, I ran a post asking how big a business referral network should be. Steve Shue, always helpful, posted a comment with links to discussions about Dunbar Numbers. Anthropologist Robin Dunbar hypothesized that a person could maintain around 150 stable relationships. Other estimates from other studies generally fall in this order of magnitude, though electronic communications may increase the number.
I have thought about Dunbar Numbers ever since and have some observations about them. First, definitions of "stable" may vary in different circumstances. For example, an auditor may only count client relationships that last many years as stable, but a professional who does many small projects, say a competitive intelligence consultant, may describe some relationships that last less than five years with the same word.
Second, not all relationships in a network are stable. We need to sort through several unstable relationships to find each one that becomes stable. Because the competitive intelligence consultant has a higher turnover rate in his core, stable network, he needs a larger pool of total relationships than the auditor does, in order to winnow through enough unstable relationships to keep sufficient stable ones. In my experience professionals with evergreen services generally don't have networks as large as those who sell project work.
Third, when a person first deliberately starts to build a network, she must winnow through a large number of unstable relationships to do so. Also, in my experience, people building a practice must actively work larger networks than those who are well established.
Fourth, we do not look for stability in every relationship. It is quite possible to network with a person for a few months or years and then find that mutual benefit from doing so declines. Networks are full of special cases for special purposes, such as the person an architect networks with to pursue work in a specific distant location once or twice in a career.
All of this is a long way of making the point that to have a good referral network, you probably need to know more people than you think you do.
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