"Dangerous" is a value judgment; the PDF is a report on journalists who were "killed, detained, held hostage, or missing." Note that this doesn't include harassment, another metric that could be possibly quantified and used to inform a theoretical "danger" ranking.
I guess what I'm leaning towards is that NBC News has a lot of spin in this piece. The headline makes you think it's about the US. The lede cites Khashoggi and tries to conflate it with general hostility towards the media in the United States, but his death was a very different situation (and different country!). Then it cites the global figure without saying "worldwide" in the paragraph, while never explicitly saying that the total death count in the US is 6. The report also shows that zero journalists were jailed in the US and zero were taken hostage.
I don't wish to minimize anyone's death. But the piece gives off a feeling that the US is becoming Saudi Arabia, yet the reason it's in this list at all is because of two events that don't really feel systemic: Capital Gazette, and hurricanes. (Could argue that mass shootings feel systemic in the US, but not mass shootings targeting journalists. No, I don't feel great trying to make that distinction.)
ADDENDUM:
How many people are working in the US as journalists? A quick search was tough to nail down. And, even with the mass shooting that hopefully proves to be a statistical anomaly, how does the deaths per 100,000 in the US compare to the 3.6 per 100,000 in the US's workplace at large?[0]
Also, edited this to remove my confusion about where Khashoggi died.
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[0]: https://247wallst.com/special-report/2018/01/02/25-most-dang...