Table 2. ARIMA Models and Events Significantly Associated With Changes in Total Gun Purchase, Handgun Permit, and Long Gun Permit Background Checks.
| Included Event (Ii)a | Month and Year | Mean (SE) Change in Gun Purchases (ωi) | P Value | Noise Model |
|---|---|---|---|---|
| Total Gun Purchases (n = 28) | ||||
| Xerox Office Building shooting, Honolulu, HI | November 1999 | 156 786.78 (67 241.97) | .01 | ARIMA(0, 1, 0)(0, 1, 1)12; (1 − B)(1 − B12)Yt = (1 − Θ1B12)at; Θ1 = −0.0931, P = .20 |
| 9/11 Attacks | September 2001 | 92 370.06 (52 746.94) | .04 | |
| Presidential election (2008) | November 2008 | 325 831.19 (53 217.05) | <.001 | |
| Geneva County, AL, shooting; Rivermark shooting, Santa Clara, CA; and Pinelake Health and Rehabilitation Nursing Home shooting, Carthage, NC | March 2009 | 11 5014.5 (53 396.9) | .02 | |
| Hartford Beer Distributors shooting, Manchester, CT | August 2010 | −108 209.14 (53 079.79) | .02 | |
| Ensley Highlands shooting, Birmingham, AL | January 2012 | −275 243.09 (55 935.05) | <.001 | |
| Chardon High School shooting, Chardon, OH | February 2012 | 175 028.33 (64 581.71) | .004 | |
| President Obama reelection (2012) | November 2012 | 243 815.45 (54 157.81) | <.001 | |
| Sandy Hook Elementary School shooting, Newtown, CT | December 2012 | 555 411.09 (53 912.86) | <.001 | |
| Los Angeles Police Department shooting and Ladera Ranch, CA shooting | February 2013 | −165 522.95 (77 891.84) | .02 | |
| Santa Monica College shooting, Santa Monica, CA | June 2013 | −123 504.57 (53 767.27) | .01 | |
| Hialeah Apartments shooting, Hialeah, FL | July 2013 | −83 221.03 (54 353.55) | .06 | |
| Cedarville Rancheria Tribal Headquarters shooting, Cedarville, CA | February 2014 | 224 893.83 (77 974.13) | .002 | |
| San Francisco Tenderloin district shooting, San Francisco, CA | March 2014 | 356 026.5 (54 065.0) | <.001 | |
| Fort Hood military base shooting, Killeen, TX, and FedEx shooting, Kennesaw, GA | April 2014 | −30 5053.78 (54 260.73) | <.001 | |
| Marysville Pilchuck High School shooting, Marysville, WA | October 2014 | −88 128.06 (54 276.28) | .05 | |
| Montgomery County, PA, shooting, Pennsburg, Souderton, Lansdale, and Harleyville, PA | December 2014 | 245 324.93 (72 903.76) | <.001 | |
| McAvan’s Pub shooting, Syracuse, NY; Douglasville, GA, shooting; and Tyrone, MO, shooting | February 2015 | −133 182.29 (68 849.47) | .03 | |
| Platte, SD, shooting and Hill Haven Event Center shooting, Greenville, GA | September 2015 | 179 574.18 (73 792.28) | .008 | |
| San Bernardino, CA, shooting and Omaha, NE, shooting | December 2015 | 872 663.84 (98 856.79) | <.001 | |
| Handgun Purchases (n = 26) | ||||
| 9/11 Attacks | September 2001 | 68 064.37 (18 857.66) | <.001 | ARIMA(3, 1, 0)(0, 1, 1)12; (1 − B)(1 − B12)Yt = (1 − Θ1B12)/ (1 − ϕ1B − ϕ2B2 − ϕ3B3)at; Θ1 = −0.3879, P < .001; ϕ1 = −0.7051, P < .001; ϕ2 = −0.2258, P = .03; ϕ3 = −0.0304, P = .38 |
| Presidential election (2008) | November 2008 | 129 894.18 (19 249.89) | <.001 | |
| Immigration Services Center shooting, Binghamton, NY | April 2009 | 367 69.45 (19 317.39) | .03 | |
| Chardon High School schooting, Chardon, OH | February 2012 | 67 258.88 (19 590.65) | <.001 | |
| Movie theater shooting, Aurora, CO | July 2012 | 43 555.85 (20 483.82) | .02 | |
| President Obama reelection (2012) | November 2012 | 69 004.86 (25 438.41) | .003 | |
| Sandy Hook Elementary School shooting, Newtown, CT | December 2012 | 361 436.25 (26 767.06) | <.001 | |
| Village of Manchester, IL, shooting | April 2013 | 32 760.11 (20 671.02) | .06 | |
| Cedarville Rancheria Tribal Headquarters shooting, Cedarville, CA | February 2014 | 100 410.94 (19 315.31) | <.001 | |
| Montgomery County, PA, shooting, Pennsburg, Souderton, Lansdale, Harleyville, PA | December 2014 | 65 592.84 (22 989.70) | .002 | |
| Tennessee Colony, TX, shooting and Minneapolis, MN, shooting | November 2015 | 122 474.56 (31 859.92) | <.001 | |
| Planned Parenthood shooting, Colorado Springs, CO | November 2015 | |||
| San Bernardino, CA, shooting and Omaha, NE, shooting | December 2015 | 344 105.74 (34 698.68) | <.001 | |
| Tampa, FL, shooting; Rochester nightclub shooting, Rochester, NY; Orlando, FL, shooting; Kalamazoo, MI, shooting; Houston, TX, drive-by shooting; Hesston, KS, shooting; and strip club shooting, Detroit, MI | February 2016 | −60 154.11 (30 970.93) | .03 | |
| Birthday party bus shooting, Chicago, IL; music video filming shooting, Chicago, IL; Halifax County, VA, shooting; and Forestville, MD, shooting | April 2016 | 60 243.83 (35 802.34) | .05 | |
| Long Gun Purchases (n = 23) | ||||
| Wedgwood Baptist Church shooting, Fort Worth, TX | September 1999 | 71 717.53 (34 028.21) | .02 | ARIMA(0, 1, 0)(1, 1, 1)12; (1 − B)(1 − B12)Yt = (1 − Θ1B12)/(1 − Φ1B12)at; Θ1 = 0.5765, P < .001; Φ1 = −0.7613, P < .001 |
| Xerox Office Building shooting, Honolulu, HI | November 1999 | 111 571.45 (32 285.38) | <.001 | |
| Radisson Bay Harbor Inn shooting, Tampa, FL | December 1999 | −151 579.31 (29 658.04) | <.001 | |
| Edgewater Technology shooting, Wakefield, MA | December 2000 | −157 279.09 (27 724.69) | <.001 | |
| 9/11 Attacks | September 2001 | 66 032.65 (26 485.92) | .006 | |
| Duquesne University shooting, Pittsburgh, PA | September 2006 | 33 892.88 (25 397.95) | .09 | |
| Presidential election (2008) | November 2008 | 145 444.96 (27 463.29) | <.001 | |
| Geneva County, AL, shooting; Rivermark shooting, Santa Clara, CA; and Pinelake Health and Rehabilitation Nursing Home shooting, Carthage, NC | March 2009 | 41 272.98 (25 720.82) | .05 | |
| Fort Hood Army Base shooting, Killeen, TX | November 2009 | −42 864.97 (27 526.48) | .06 | |
| Chardon High School shooting, Chardon, OH | February 2012 | 69 056.38 (27 276.71) | .006 | |
| President Obama reelection (2012) | November 2012 | 132 521.49 (26 574.07) | <.001 | |
| Sandy Hook Elementary School shooting, Newtown, CT | December 2012 | 263 346.05 (26 700.57) | <.001 | |
| Los Angeles Police Department shooting and Ladera Ranch, CA, shooting | February 2013 | −48 703.25 (27 543.76) | .04 | |
| Mohawk Village and Herkimer Village, NY, shooting | March 2013 | 54 162.67 (25 985.47) | .02 | |
| San Bernardino, CA, shooting and Omaha, NE, shooting | December 2015 | 135 638.1 (35 809.0) | <.001 | |
| Birthday party bus shooting, Chicago, IL; music video filming shooting, Chicago, IL; Halifax County, VA, shooting; and Forestville, MD, shooting | April 2016 | 77 161.4 (38 076.09) | .02 | |
Abbreviations: ARIMA, autoregressive integrated moving average; at, random error; B, backward shift operator; Ii, given interruption; Yt, current time-series observation; Θ, seasonal moving-average operator; ϕ, autoregressive operator; Φ, seasonal autoregressive operator; ωi, ARIMA coefficient corresponding to Ii.
a
When more than 1 event occurred in the same month, only 1 effect size was calculated per month. The intervention model for all included events is Yt* = at + Σ(Ii × ωi).