Media coverage and firearm acquisition in the aftermath of a mass shooting


With an alarming frequency, the United States is experiencing mass shooting events, which often result in heated public debates on firearm control. Whether such events play any role in recent dramatic increases in firearm prevalence remains an open question. This study adopts an information-theoretic framework to analyse the complex interplay between the occurrence of a mass shooting, media coverage on firearm control policies and firearm acquisition at both national and state levels. Through the analysis of time series from 1999 to 2017, we identify a correlation between the occurrence of a mass shooting and the rate of growth in firearm acquisition. More importantly, a transfer entropy analysis pinpoints media coverage on firearm control policies as a potential causal link in a Wiener–Granger sense that establishes this correlation. Our results demonstrate that media coverage may increase public worry about more stringent firearm control and partially drive increases in firearm prevalence.

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Fig. 1: Time series for the study of the relationships between firearm acquisition, mass shootings and media coverage on firearm control policies from January 1999 to December 2017.
Fig. 2: Estimated conditional transfer entropy between each pair of mass shootings, media output and firearm background checks.
Fig. 3: Restrictiveness of firearm-related laws and transfer entropy from media coverage on firearm control polices to background checks, after controlling for mass shootings.

Data availability

All data needed to evaluate the paper’s conclusions are presented in the article and the Supplementary Information, as well as being freely available at

Code availability

The code used to reproduce the results is freely available at


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We acknowledge D. Silver from New York University for useful input. M.P. thanks M. Camacho from the University of Murcia, Murcia, Spain, for his kind help with the use of TRAMO-SEATS, and M. Ruiz Marín from Technical University of Cartagena, Murcia, Spain, for stimulating discussions. R.S. acknowledges the hospitality of the Mechanical and Aerospace Engineering Department at New York University, Tandon School of Engineering during his sabbatical leave. Finally, M.P. thanks N. Simons and the Rockefeller Institute for useful discussions on data collection and policy making about firearm violence. This project was supported in whole by a grant from the New York University Research Challenge Fund Program. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Author information

S.N. and M.P. designed the research. R.R.S. collected the data. All authors contributed to the formulation of the hypotheses underlying the study. S.N., M.P., R.R.S. and R.S. conducted the analysis. M.P. wrote the first draft of the manuscript. All authors discussed the results and edited the final version of the manuscript.

Correspondence to Maurizio Porfiri.

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Supplementary Notes, Supplementary References, Supplementary Figures 1–16, and Supplementary Tables 1–5.

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