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David White
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What's the variance in the Six Degrees model?

Recall the six degrees of Kevin Bacon game. You can even play the game at The Oracle of Bacon, and their search works via Breadth First Search.

I interpret the punchline as saying that if I start with a random actor I can "usually" get to Kevin Bacon with six steps. So perhaps there's a probability distribution over all starting actors and the expected number of steps to Kevin Bacon is less than six.

Does anyone know the variance of this probability distribution?

I would be satisfied with either a theoretical answer or a data-driven answer. The former might look like a reference to a paper where someone proposed a graph that acts like IMDB and has studied the search problem on it. This is related to a question my student recently asked, and it seems the type of graph which most closely represents IMDB might be an intersection graph.

The latter type of answer might come from a query to the IMDB database. Their data is publicly available and I'm waiting for a confirmation from them that it can be used for academic purposes. The Oracle of Bacon website links to the FTPs where you can get the IMDB data. My student and I can do this analysis, but I wanted to post a question here first to see if someone else had already done it.

We need the variance for a step in our current research project. Thanks!

David White
  • 30.3k
  • 9
  • 154
  • 250