As promised, following is my report on the reach and efficiency of LinkedIn networks.

For 3 weeks, I've collected network stats from 113 LinkedIn users who responded to my original blog and my LinkedIn question. I tabulated the following data for each respondent:

1^st Level Connections - Your trusted friends and colleagues

2^nd Level Connections - Friends of friends (two degrees away from you)

3^rd Level Connections - Their friends (three degrees away from you)

Total users you can contact through an Introduction (Reach)

Reach is easy. It's the total number of users you can contact on LinkedIn through an introduction. Glenn Gutmacher has the largest reach with almost 7 million people. Five other people also can reach over 6 million people including Dave Mendoza & Maureen Sharib. I was surprised to find that the person with the second largest reach isn't a recruiter or sourcer. Alex Zaretsky is an embedded software engineer from the UK. Seven people can reach between 5 million and 6 million including Vincent Wright and me. Seventeen people can reach between 4 million and 5 million, 16 people can reach between 3 million and 4 million, and 24 people can reach between 2 million and 3 million. The bottom line on reach is that lots of people can reach really large numbers of people!

Efficiency isn't as easy as reach. Shally Steckerl defined The Promiscuity Ratio (efficiency) as your first degree contacts divided by the total number of contacts you can reach. So, for example, if you have 100 first degree contacts and can reach 1 million total contacts, you network would have an efficiency of 0.0001. I tired quickly of working with such small numbers so I arbitrarily multiplied Shally's ratio by 1,000. So the efficiency of the network used in our example can be represented as 0.1.

Enough of the example, let's look at some real network efficiencies. It turns out that 42 of the 113 people who responded have networks that are more efficient than the example given above. The most efficient network belongs to Robert Pilkey (0.02) who leverages just 26 first level contacts to a reach of almost 1.4 million! The seven most efficient networks all have less than 100 level one contacts. The 50 most efficient networks all have less than 500 level one contacts. The 90^th most efficient network is the first with over 1,000 level one contacts.

So what is the efficiency of those networks with the greatest reach? Sure enough, they rank towards the bottom: Dave Mendoza (1.09), Glenn Gutmacher (0.86), Alex Zaretsky (0.61), Vincent Wright (0.30), and me (0.24). It seems clear that the larger your network the more likely that it will be less efficient.

Should you care about reach and efficiency? Let's look at a few examples:

1) If you are a recruiter or sourcer you probably want to maximize your reach. You want to be able to connect with as many people as possible. The more connections you have the more likely you'll have something to leverage for every search. There are, no doubt, exceptions to this rule. If you specialize in a very narrow area, you may only want to have people in that area in your network. However, for most people, the more the merrier and efficiency be damned!

2) If you are a business professional outside of the fields of recruiting, sourcing, marketing, or sales, you probably want to have only people in your network who have experience in some way related to your profession. These are the folks who maintain that it's best to connect with only people you know. People in this category probably don't care much about reach. I doubt that they care much about efficiency either. Their main focus will be on their level one contacts. Of course when it comes time to find a new job, these folks may wish that they were connected with professional recruiters and sourcers with large networks.

3) Some people are extremely concerned with adding anything to their life that could be construed as more work. People in this group may be concerned with the number of LinkedIn related messages and requests that they may receive if their network gets too large. They may choose to limit their network reach for this reason. I have a large network and I've found that it is quite manageable. The trick, for me, is to read almost all of my LinkedIn messages on LinkedIn instead of in my email. That way I can handle them whenever I choose. I find that I can handle everything in less than 10 minutes a day. Click on Account & Settings under You at the bottom of your LinkedIn home page and look under Receiving Messages for all the settings.

In conclusion, reach seems to be the most relevant measure when building a LinkedIn network. Each person should work out for themselves what they plan to achieve by investing time and effort in the pursuit. Efficiency, while interesting, doesn't seem to have any real-world application. LinkedIn network efficiency is likely to decline as the network grows and matures. It is theoretically possible to build a high reach and high efficiency network by connecting only with people with large networks. I doubt that this is a useful goal in the long run but it is a great approach to take to grow reach quickly when getting your network started.

Thank you to everyone who participated in this survey. Much appreciated!