http://www.latimes.com/news/local/la-me-immunization29-2009mar29,0,3148179.story?page=1 California Schools have recently seen a large rise in the number of elementary school students who are not receiving immunizations. Although these students still only make up a small percentage overall, parents who do not immunize their children are likely to send their children to the same school. Many of these parents fear that vaccinations could lead to their children developing other conditions such as autism, even though a federal court has recently ruled otherwise. If a high percentage of a group is immunized, the non-immunized are usually protected by what is known as “herd immunity.” Currently 1 in 11 elementary schools in California lack the percentages necessary to maintain herd immunity, and are at risk of having a serious outbreak. The rise in parents choosing not to immunize their children can be seen as the result of an information cascade.

When a network of people is supplied with unproven or biased information, the members of the network can easily be swayed towards a certain opinion via information cascading. Let us imagine there is closely nit group of kindergarten parents, who meet regularly to discuss issues. Most of these individuals are first time parents, and know very little about immunizations and diseases. If they live in a somewhat small town, and have indifferent physicians, a medical trend could easily go unchallenged. One day one of the mother’s brings up that she has decided not to immunize her child, because of an interview she saw while watching Fox News. The other parents in the group, who are currently faced with the same decision, and lack a competing source of perspective, may also be swayed to not immunize. These parents believe that there will be a bigger payoff in the healthiness of their child if he or she is not immunized. As more parents in this group decided not to immunize their children, the more likely other parents will not immunize their children due to the number of their acquaintances who made the same decision. Imagine that some new parents now move into the neighborhood, and are going to enroll their child in kindergarten. Keeping with the format from our Econ 2040 class, the signal, or information provided to these parents, can be though of as the sum of the parent’s prior knowledge and perspectives on the subject of immunization. By speaking to other parents, these new parents learn the choices that the other parents made on whether or not to immunize their children. However, these new parents do not really know the knowledge (signal), off which these other parents based their decision. These new parents may end up not immunizing their child, due to an information cascade.