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The Spread of Steroids in Baseball
When the Mitchell Report, on steroid use in Major League Baseball [MLB], was published, people were surprised at who and how many players were mentioned. The diagram below shows a human network created from data found in the Mitchell Report. Baseball players are shown as green nodes. Those who were found to be providers of steroids and other illegal performance enhancing substances appear as red nodes. The links reveal the flow of chemicals -- from provider to player.
Figure 1 - Steroid Supply Chain Network
To understand what is happening in a human group, we need to look at more than one network. Ideas, gossip, opinions and advice flow between people that know each other -- the informal networks of trust. To know what is happening and who is doing what, you need to be part of many social networks.
Through player trades and free-agent signings, MLB does a good job of building social networks. With players constantly changing teams, they form new links with new teammates, while maintaining many of their old ties to former teammates. This activity quickly creates a densely interconnected social network. What happens inside a tightly connected network? Information moves quickly over short paths and similar messages are heard again and again via redundant links. Everyone knows the same thing at the same time -- which gives everyone in the network the impression that "this must be how it is."
Figure 2 - There are No Silos in Baseball
Figure 2 shows the same players as in Figure 1 -- only the links have changed to show different relationships between the nodes/players. Now, two players are connected if they played for the same team at the same time -- a thicker line connects players who spent more time together as teammates. This network reveals the dense connections in MLB that formed via frequent player movement between teams.
Figure 3 below shows three teams that had more than a handful of players named in the Mitchell Report. The magenta colored links show intra[within]team ties, while the gray links show inter[between]team ties. Naturally, the network is denser within a team than between teams. This "small-world" network pattern creates a very efficient network for moving information [who's doing it?] and knowledge [how do I take advantage of it?] throughout MLB.
Figure 3 - Social Connectivity Within and Between Teams
MLB players live and play in very efficient social networks. Applying network metrics to the MLB data, we see that most MLB players are within 3 steps of each other, while many are within 2 steps. If steroids are happening within baseball, just about everyone knows it, even if they do not know who all of the individual participants are.
If the MLB network structure allows everyone to know what is happening, the Mitchell investigators must have had an easy time interrogating players, right? Wrong -- a close network also implies conformity. To remain a member of the network you play by the local rules. As in many groups where members are aware of illegal activity, one of the strongest informal rules is "don't talk." People in dense groups conform willingly -- they do not want to be pruned from the network.
On the other hand, people with connections to multiple groups are not so constrained -- expulsion from one group usually does not affect their membership in other groups. Baseball players did not have this option of multiple group membership -- if they wanted to play, they had to remain silent. It was OK to talk about it, as long as it was within the group. This was one of the factors that allowed steroid use to grow and persist through the recent years and why outsiders have had such a hard time figuring out what is really going on.
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Online Research: Silvija Krebs | Copyright © 2008, Valdis Krebs