Internet search patterns reveal firearm sales, policies, and deaths

Abstract

Firearm-related violence is a leading cause of morbidity and mortality and is at the center of a major public health and policy debate in the United States. Despite the critical role of data in informing this debate, accurate and comprehensive data on firearm sales and ownership is not readily available. In this study, we evaluate the potential of using firearm-related internet search queries as a complementary, freely available, and near-real-time data source for tracking firearm sales and ownership that enables analysis at finer geographic and temporal scales. (Here, we examine data by state and by month to compare with other data sources, but search engine volume can be analyzed by city and by the week or by day). We validate search query volume against available data on background checks in all 50 US states, and find that they are highly correlated over time (Pearson's r = 0.96, Spearman's ρ = 0.94) and space (Pearson's r = 0.78, Spearman's ρ = 0.76). We find that stratifying this analysis by gun type (long-gun vs. handgun) increases this correlation dramatically, across both time and space. We also find a positive association between firearm-related search query volume and firearm-related mortality (Pearson's r = 0.87, Spearman's ρ = 0.90), and a negative association with the strength of state-level firearm control policies (Pearson's r = -0.82, Spearman's ρ = -0.83). Based on these findings, we propose a framework for prospective surveillance that incorporates firearm-related internet search volume as a useful complementary data source to inform the public health policy debate on this issue.

Fig. 1. Monthly comparison of background checks vs. search volumes.

a U.S. long-gun background checks vs. U.S. relative Internet search volume for the term shotgun (Pearson’s r = 0.96, Spearman’s ρ = 0.94) and b U.S. handgun background checks vs. U.S. relative Internet search volume for the term 9 mm in 2019 (Pearson’s r = 0.97, Spearman’s ρ = 0.94).

Fig. 2. Time-lagged correlations of search volume vs. backgrround checks.

a Internet search volume for “shotgun” and long-gun background checks in 2019. b Internet search volume for “9 mm” and handgun background checks in 2019.

Fig. 3. State-by-state comparisons of background checks vs. search volumes.

a U.S. long-gun background checks vs. U.S. relative Internet search volume for the term shotgun (Pearson’s r = 0.78, Spearman’s ρ = 0.76). b U.S. handgun background checks vs. U.S. relative search Internet search volume for the term 9 mm (Pearson’s r = 0.63, Spearman’s ρ = 0.59) across all 50 US states in 2019.

Fig. 4. State-by-state comparisons of firearm deaths vs. search volumes.

a Firearm-related deaths per 100,000 people vs. relative Internet search volume for shotgun (Pearson’s r = 0.71, Spearman’s ρ = 0.68). b Firearm-related deaths per 100,000 people vs. relative Internet search volume for 9 mm (Pearson’s r = 0.87, Spearman’s ρ = 0.90) across all 50 US states in 2017.

Fig. 5. Geographic view of firearm deaths and search volumes.

a Firearm-related deaths per 100,000 residents b Relative search volume for the term shotgun. c Relative search volume for the term 9mm across all 50 US states in 2017. All maps produced with Plotly version 4.11, available through an MIT License (https://github.com/plotly/plotly.js/blob/master/LICENSE).

Fig. 6. State-level firearm policies vs. search volume.

a Restrictiveness of state-level firearm policies, based on The Giffords Law Center to Prevent Gun Violence 2019 Annual Gun Law State Scorecard (1–50 scale) vs. Internet search volume for the terms shotgun (Pearson’s r = 0.76, Spearman’s ρ = −0.78). b The same analysis shown for the search term 9 mm (Pearson’s r = −0.82, Spearman’s ρ = −0.83). All data from 2019.

Fig. 7. Geographic view of state-level firearm policies.

Restrictiveness of state-level firearm policies across all 50 US states based on The Giffords Law Center to Prevent Gun Violence 2019 Annual Gun Law State Scorecard (1–50 scale). All maps produced with Plotly version 4.11, available through an MIT License (https://github.com/plotly/plotly.js/blob/master/LICENSE).

Fig. 8. Analysis and search term correlation plots.

Correlation plots and corresponding Pearson’s r and Spearman’s ρ values for all analyses and all search terms.