Follow-up to "Media bias against Muslims in terrorism coverage"

The Kearns et al. study "Why Do Some Terrorist Attacks Receive More Media Attention Than Others?" has been published in Justice Quarterly; the abstract indicates that "Controlling for target type, fatalities, and being arrested, attacks by Muslim perpetrators received, on average, 357% more coverage than other attacks". A prior Kearns et al. analysis was reported on in a 2017 Monkey Cage post and a paper posted at SSRN with a "last edited" date of 3/5/17 limited to "media coverage for terrorist attacks in the United States between 2011 and 2015" (p. 7 of the paper).

Data for the Kearns et al. study published in Justice Quarterly has been expanded to cover terrorist attacks from 2006 to 2015 (instead of 2011 to 2015) and now reports a model with a predictor for "Perpetrator and group unknown", with a p-value under 0.05 for the Muslim perpetrator predictor. Footnote 9 of Kearns et al. 2019 discusses selection of 2006 as the starting point:

Starting in 2006, an increasing percentage of Americans used the Internet as their main source of news [URL provided, but omitted in this quote]. Since the news sources used for this study include both print and online newspaper articles, we started our analysis in 2006. In years prior to 2006, we may see fewer articles overall since print was more common and is subject to space constraints (p. 8).

That reason to start the analysis in 2006 does not explain why the analysis in the Monkey Cage post and the 3/5/17 paper started in 2011, given that the news sources in these earlier reports of the study also included both print and online articles.

In this 3/28/17 post, I reported that the Muslim perpetrator predictor had a 0.622 p-value in my analysis predicting the number of articles of media coverage using the Kearns et al. 2011-2015 outcome variable coding, controlling for the number of persons killed in the attack and for whether the perpetrator was unknown.

Using the 2006-2015 dataset and code that Dr. Kearns sent me upon request, I ran my three-predictor model, limiting the analysis to events from 2011 to 2015:

The above p-value for the Muslim perpetrator predictor differs from my 0.622 p-value from the prior post, although inferences are the same. There might be multiple reasons for the difference, but the 3/5/17 Kearns et al. paper reports a different number of articles for some events; for example, the Robert Dear event was coded as 204 articles in the paper and as 178 articles in the 2019 article, and the number of articles for the Syed Rizwan Farook / Tashfeen Malik event dropped from 179 to 152.

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The inference about the Muslim perpetrator predictor is more convincing using the 2006-2015 data from Kearns et al. 2019 than from the 2011-2015 data: the 2006-2015 data produce a 2.82 Muslim perpetrator predictor t-score using my three-predictor model above and a 4.20 t-score with a three-predictor model replacing the number killed in the event with a predictor for whether someone was killed in the event.

For what it's worth, along with higher-than-residual news coverage for events with Muslim perpetrators, the Kearns et al. data indicate that, compared to other events with a known perpetrator, events with Muslim perpetrators also have higher-than-residual numbers of deaths, numbers of logged wounded, and (at least at p=0.0766) likelihood of a death:

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NOTES

1. I could not find the 3/5/17 Kearns et al. paper online now, but I have a PDF copy from SSRN (SSRN-id2928138.pdf) that the above post references.

2. Stata code for my analyses:

gen PerpUnknown=0
replace PerpUnknown=1 if eventid==200601170007
replace PerpUnknown=1 if eventid==200606300004
replace PerpUnknown=1 if eventid==200607120007
replace PerpUnknown=1 if eventid==200705090002
replace PerpUnknown=1 if eventid==200706240004
replace PerpUnknown=1 if eventid==200710200003
replace PerpUnknown=1 if eventid==200710260003
replace PerpUnknown=1 if eventid==200802170007
replace PerpUnknown=1 if eventid==200803020012
replace PerpUnknown=1 if eventid==200803060004
replace PerpUnknown=1 if eventid==200804070005
replace PerpUnknown=1 if eventid==200804220011
replace PerpUnknown=1 if eventid==200806140008
replace PerpUnknown=1 if eventid==200807250030
replace PerpUnknown=1 if eventid==200903070010
replace PerpUnknown=1 if eventid==200909040003
replace PerpUnknown=1 if eventid==201007270013
replace PerpUnknown=1 if eventid==201011160004
replace PerpUnknown=1 if eventid==201101060018
replace PerpUnknown=1 if eventid==201102220009
replace PerpUnknown=1 if eventid==201104230010
replace PerpUnknown=1 if eventid==201105060004
replace PerpUnknown=1 if eventid==201109260012
replace PerpUnknown=1 if eventid==201110120003
replace PerpUnknown=1 if eventid==201205200024
replace PerpUnknown=1 if eventid==201205230034
replace PerpUnknown=1 if eventid==201208120012
replace PerpUnknown=1 if eventid==201301170006
replace PerpUnknown=1 if eventid==201302260036
replace PerpUnknown=1 if eventid==201304160051
replace PerpUnknown=1 if eventid==201304170041
replace PerpUnknown=1 if eventid==201304180010
replace PerpUnknown=1 if eventid==201307250065
replace PerpUnknown=1 if eventid==201308220053
replace PerpUnknown=1 if eventid==201403180089
replace PerpUnknown=1 if eventid==201403250090
replace PerpUnknown=1 if eventid==201406110089
replace PerpUnknown=1 if eventid==201410030065
replace PerpUnknown=1 if eventid==201410240071
replace PerpUnknown=1 if eventid==201411040087
replace PerpUnknown=1 if eventid==201502170127
replace PerpUnknown=1 if eventid==201502230104
replace PerpUnknown=1 if eventid==201503100045
replace PerpUnknown=1 if eventid==201506220069
replace PerpUnknown=1 if eventid==201506230056
replace PerpUnknown=1 if eventid==201506240051
replace PerpUnknown=1 if eventid==201506260046
replace PerpUnknown=1 if eventid==201507150077
replace PerpUnknown=1 if eventid==201507190097
replace PerpUnknown=1 if eventid==201508010105
replace PerpUnknown=1 if eventid==201508020114
replace PerpUnknown=1 if eventid==201508190040
replace PerpUnknown=1 if eventid==201509040048
replace PerpUnknown=1 if eventid==201509300082
replace PerpUnknown=1 if eventid==201512260016
tab PerpUnknown, mi
tab PerpUnknown PerpMuslim, mi
tab PerpUnknown PerpNonMuslim, mi
tab PerpUnknown PerpGroupUnknown, mi
nbreg TOTALARTICLES PerpMuslim numkilled PerpUnknown if eventid>=201101060018
nbreg TOTALARTICLES PerpMuslim numkilled PerpUnknown
gen kill0=0
replace kill0=1 if numkilled==0
tab numkilled kill0
nbreg TOTALARTICLES PerpMuslim kill0     PerpUnknown
ttest numkilled if PerpUnknown==0, by(PerpMuslim)
ttest numkilled                  , by(PerpMuslim)
ttest logwound  if PerpUnknown==0, by(PerpMuslim)
ttest logwound                   , by(PerpMuslim)
prtest kill0    if PerpUnknown==0, by(PerpMuslim)
prtest kill0                     , by(PerpMuslim)

3. Kearns et al. 2019 used a different "unknown" perpetrator measure than I did. My PerpUnknown predictor (in the above analysis and the prior post) coded in a dichotomous variable as 1 any perpetrator listed as "Unknown" in the Kearns et al. list. Kearns et al. 2019 has a dichotomous PerpGroupUnknown variable that differentiated between perpetrators in which the group of the perpetrator was known (such as for this case with an ID of 200807250030 in the Global Terrorism Database, in which the perpetrators were identified as Neo-Nazis) and perpetrators in which the group of the perpetrator was unknown (such as for this case with an ID of 200806140008 in the Global Terrorism Database, in which the perpetrator group was not identified). Kearns et al. 2019 footnote 17 indicates that "Even when the individual perpetrator is unknown, we often know the group responsible so 'perpetrator unknown' is not a theoretically sound category on its own, though we account for these incidents in robustness checks"; however, I'm not sure why "perpetrator unknown" is not a theoretically sound category on its own for the purpose of a control when predicting media coverage: if a perpetrator's name is not known, then there might be fewer news articles because there will be no follow-up articles that delve into the background of the perpetrator in a way that could be done if the perpetrator's name were known.