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What percentage of US mass shootings are linked to left-wing extremists?
Executive Summary
The available analyses converge on a clear finding: left-wing extremists account for a small minority of U.S. extremist-related mass killings and politically motivated murders, while right-wing extremists account for the majority of deaths in recent years. Reports and syntheses from 2024–2025 show right-wing actors responsible for roughly 75–80% of domestic terrorism deaths since 2001, with left-wing actors representing a much smaller share of incidents and fatalities [1] [2] [3].
1. What claimants said — the competing statements that set the question on fire
The set of analyses extracts several related claims: the ADL reports note that most extremist-related mass killings in 2022 and 2024 were committed by right-wing extremists, with no recorded left-wing extremist murders in those specific years [1] [4]. Cato’s compilation frames left-wing actors as responsible for a small slice of politically motivated murders historically—about 2% since 1975 and a higher share, about 22% since 2020, in a subset measure—showing differing denominators and time windows shape headline percentages [5]. Other summaries and media analyses put left-wing incidents at roughly 10–15% of incidents but under 5% of fatalities, while attributing 75–80% of deaths to right-wing violence since 2001 [2] [3]. These differing claims highlight how percentages depend on definitions, years, and whether incidents or fatalities are counted [6] [7].
2. The numbers themselves — what the evidence actually reports about percentages
When analysts report percentages, they use different bases: incidents, fatalities, or politically motivated murders across long time spans. The ADL’s 2022 and 2024 snapshots show zero left-wing extremist murders in those specific reporting years and a dominance of right-wing murderers (published 2025-06-20 and 2025-02-10 respectively) [1] [4]. Broader syntheses place left-wing share of incidents at about 10–15% but their share of deaths under 5%, while right-wing actors are credited with about three-quarters to four-fifths of domestic terrorism deaths since 2001 [2] [3]. Cato’s analysis measures politically motivated murders differently and reports 65 deaths by left-wing actors since 1975 (≈2% of that tally) but notes a higher proportion in the post-2020 subset [5]. The bottom line is that left-wing extremists comprise a small minority by most standard measures [6] [2].
3. Why percentages diverge — methodological fault lines that change the story
The divergent percentages stem from definition choices, time windows, and whether analysts count plots, incidents, or fatalities. Some work focuses on extremist-related mass killings in a single year (ADL snapshots for 2022 and 2024), while others aggregate decades of politically motivated murders (Cato) or domestic terrorism deaths since 2001 (PBS and related analyses) [1] [4] [5] [2]. The CSIS-related debate and NPR coverage emphasize that small absolute numbers and subjective coding of ideological motivation make short-term shifts unstable; a handful of incidents can swing percentages substantially [7]. This methodological sensitivity means headline percentages can be true in context but misleading if readers miss the definition and period used [6] [7].
4. Recent trends and contested developments — why 2024–2025 drew new attention
Recent reporting through 2024–2025 intensified scrutiny: ADL noted consecutive years dominated by right-wing perpetrators (2022 and 2024), while some 2025 studies flagged a rise in far-left plots in a short window, prompting debate over sample size and coding [1] [4] [7]. Analysts caution that a small cluster of left-wing-coded incidents in a half-year can look like a “rise” despite small absolute counts, and that critics question subjectivity in labeling and the political stakes of highlighting one ideological trend over another [7]. This dispute shows how selective counting and the timing of incidents shape political narratives and policy responses [6] [7].
5. Bottom line for the original question — a measured, source-grounded answer and the caveats
Answering “what percentage of US mass shootings are linked to left-wing extremists?” requires a qualifier: by the most consistent measures used in the cited analyses, left-wing extremists account for a small minority of extremist-related mass killings and fatalities — generally single-digit percentages of deaths and roughly 10–15% of incidents in some compilations, whereas right-wing extremists account for the majority of deaths (~75–80% since 2001) [2] [3] [6]. The strongest caveat is methodological: percentages flip depending on definitions, timeframes, and whether counts emphasize incidents, plots, or fatalities, and short-term upticks in small samples can be misread as long-term trends [5] [7].