According to data available from START, The National Consortium for the Study of Terrorism and Responses to Terrorism, there were 174 global terrorism deaths in 1970, and 22,847 deaths due to terrorism in 2020. The most deadly year between 1970 and 2020 was 2014, with 44,684 deaths.
Even though between 2014 and 2020 the number of deaths due to terrorism has declined by 50%, the overall trend over the 50-year period is definitely upwards. It might be reasonable to assert that deaths due to terrorism have "dropped significantly in the last 6 - 8 years", or something similar. Over the last 50 years, "plummeted" does not seem at all like an accurate characterization.
For anyone curious about the criteria for "terrorism" and "death" in the data, here is a quote regarding the criteria used by START for the data set:
A terrorist incident is included in GTD if it is the following:
- The incident must be intentional – the result of a conscious calculation on the part of a perpetrator.
- The incident must entail some level of violence or immediate threat of violence -including property violence, as well as violence against people.
- The perpetrators of the incidents must be sub-national actors. The database does not include acts of state terrorism.
In addition, at least two of the following three criteria must be present for an incident to be included in the GTD:
- Criterion 1: The act must be aimed at attaining a political, economic, religious, or social goal. In terms of economic goals, the exclusive pursuit of profit does not satisfy this criterion. It must involve the pursuit of more profound, systemic economic change.
- Criterion 2: There must be evidence of an intention to coerce, intimidate, or convey some other message to a larger audience (or audiences) than the immediate victims. It is the act taken as a totality that is considered, irrespective of whether every individual involved in carrying out the act was aware of this intention. As long as any of the planners or decision-makers behind the attack intended to coerce, intimidate or publicize, the intentionality criterion is met.
- Criterion 3: The action must be outside the context of legitimate warfare activities. That is, the act must be outside the parameters permitted by international humanitarian law (particularly the prohibition against deliberately targeting civilians or non-combatants).
Is it defined as a suicide attack?
This variable is coded “Yes” in those cases where there is evidence that the perpetrator did not intend to escape from the attack alive.
Successful vs. unsuccessful attacks:
"The GTD does include attacks that were attempted but ultimately unsuccessful. The circumstances vary depending on tactics (for details see the success variable, below). However, in general, if a bomb is planted but fails to detonate; if an arsonist is intercepted by authorities before igniting a fire; or, if an assassin attempts and fails to kill his or her intended target, the attack is considered for inclusion in the GTD, but denoted as unsuccessful.
The success of a terrorist strike is defined according to the tangible effects of the attack. Success is not judged in terms of the larger goals of the perpetrators. For example, a bomb that exploded in a building would be counted as a success even if it did not succeed in bringing the building down or inducing government repression. The definition of a successful attack depends on the type of attack. Essentially, the key question is whether or not the attack type took place. If a case has multiple attack types, it is successful if any of the attack types are successful, with the exception of assassinations, which are only successful if the intended target is killed."
Fatalities are defined as:
"The total number of confirmed fatalities for the incident. The number includes all victims and attackers who died as a direct result of the incident. Where there is evidence of fatalities, but a figure is not reported or it is too vague to be of use, this field remains blank. If information is missing regarding the number of victims killed in an attack, but perpetrator fatalities are known, this value will reflect only the number of perpetrators who died as a result of the incident. Likewise, if the information on the number of perpetrators killed in an attack is missing, but victim fatalities are known, this field will only report the number of victims killed in the incident."
"The number of confirmed non-fatal injuries to both perpetrators and victims."