Association for Public Policy Analysis & Management

This paper thus aims to fill this gap in the literature by being the first to estimate the impact of fake news on individuals. I do so by using the unexpected surge in the media coverage on the false claim that MMR (Measles-Mumps-Rubella) vaccines cause autism in 2007, as an exogenous shock in fake news to parents. This exogenous shock in misinformation, along with the fact that some parents are ex-ante more likely to be sensitive to this misinformation than the others, allows me to identify the effects of false news about vaccine safety on parents’ vaccination decision using a difference-in-difference approach.

I use coverage on major television networks as a proxy for media coverage. I analyze news transcripts of 6 major television networks in the US (ABC, CBS, NBC, CNN, MSNBC, and Fox News) from 2001-2012 from LexisNexis and found that the number of false news about vaccine safety rose dramatically in 2007. To identify the effects of fake news, I use the 2002-2012 National Immunization Survey data with a difference-in-differences approach to compare children who are most likely to be treated by the increase in fake news to those who are least likely to. I determine children’s sensitivity to false news about vaccines and autism based on whether child is a firstborn, child’s gender, and parents’ age. This is because older parents and parents of boys are more likely to be concerned about autism risk as it is well reported that autism is 4 times more common among boys than girls and children of older parents could be as much as 5 times as likely to have autism than children of younger parents. And experienced parents are more likely to have already formed their opinion on the issue and less likely to be receptive to the new misinformation than new parents.

Results show that the surge in fake news led to a drop of 3.27 percentage points in MMR vaccine take-up rate at 15 months old and a drop of 4.13 percentage points at 29 months old. Since the results show a drop at both ages, they indicate that fake news did not only cause parents to delay giving their children the MMR shot but completely refuse the MMR shot altogether. My results show that the media is powerful and that completely incorrect information, when reported by the media, can change individual behavior, even when it is very easy to verify that the information is wrong.