Information Cascade While Going to NU Wrigley Day

I was on the El going to Wrigley Field during NU Wrigley Day and I saw information cascade happen in action. I was on the purple express going South from NU. The purple express stops at the Addison stop (where Wrigley Field is) during game day. The El trains are made up of compartments with each compartment having two sets of doors on each end.

Anyways, when the train stopped at the Howard stop, people started getting off. I told the people around my door that the train is going to Addison and everyone around me stayed on the train but everyone at the other door got off. One person on the other door who left started an information cascade because one or two people followed him and then everyone else assumed they knew what they were doing and followed as well. On my side people were going to leave because they saw the other people leaving but me telling them that the train is continuing down to Addison also created an information cascade and everyone on my side stayed. Shows how a few people can have a big impact on how group acts.

As a resident of Chicago, I've seen this happen a lot, especially during the summer when I would take Purple line back home after working at Northwestern. Many people do not realize that during rush hour, the Purple Line runs an express route that travels from Howard to Belmont, then takes follows the Brown line tracks. As mentioned above, during Cubs day game, the Purple line stops at Sheridan which is like 3 blocks from Wrigley.

The cascade mentioned above starts at the Howard stop where Cubs fans either get off and go onto the red line, and therefore have to suffer through going on every stop on the red line or they stay on the Purple line and the next stop for them is Sheridan, with no other trains in front of them preventing a slow down.

We can think of bunch of friends traveling together as one cluster. So usually there are many clusters of cubs fan traveling to the game on the same car. A weak tie between clusters can be represented as a person from one cluster overhearing another person speak from a different cluster, since everyone is so close inside a train car, this happens a lot. What occurs during cubs day games at the Howard is that there is usually one cluster where one of the friends says we'll stay on the purple line because it goes straight to Sheridan and they'll get their faster. Since the value of staying on the Purple line is much greater than that of switching over the Red line, the friends all agree to this idea, so a cascade just occurred within the cluster. Now if someone from a different cluster overhears this, they are open to the idea of spending less time on the train and tell friends within their own cluster. This time there is a larger threshold because sometimes the friend don't believe that the Purple line stops at Sheridan (as many people actually don't) so they are unsure whether to switch to the Red line or run the risk of possibly getting off on Belmont and walking to Addison. A cascade may start depending on whether the friends in the cluster accept this notion. However, sometimes there is an outside signal, represented as a weak tie, if the conductor of the train actually announces that the train is going to stop on Sheridan (sometimes the conductors do, sometimes they don't). If the conductor does mention this, then the second cluster of friends, now with outside information, accept the behavior of staying on the Purple and so a cascade just occurred. This can go on throughout the train but doesn't spread from cluster to cluster between different cars because of physical constraints, much like a network where there is no bridge between two strongly connected components.