"Major" is somewhat fuzzy, but for now I'm thinking 20 killed OR 100 injured.
Last one per wikipedia would have been in 2017, so per Laplace rule of succession prior should in some sense be 1/(2025 - 2017 + 2) = 10%.
References:
https://www.politico.eu/article/uk-police-arrest-terror-probe-iran-terrorism-investigations/,
https://www.telegraph.co.uk/news/2025/05/04/iranian-terror-attack-uk-hours-away-from-being-launched/,
https://en.wikipedia.org/wiki/Terrorism_in_Europe#Deadliest_attacks
Update 2025-05-06 (PST) (AI summary of creator comment): The creator has clarified that the primary criteria for an event to resolve this market are:
It is a terrorist attack in Europe.
It results in 20 killed OR 100 injured.
An event meeting these criteria will count even if it is not listed on the specific Wikipedia page (Terrorism in Europe#Deadliest_attacks) that was referenced in the original description (in the context of baserate calculation). The 2024 Magdeburg car attack was provided as an example of such an event that would count.
Update 2025-11-15 (PST) (AI summary of creator comment): An attack does not need to be officially charged as terrorism to count for resolution. Any attack that meets the criteria (20 killed OR 100 injured) will resolve this market positively, regardless of whether it is prosecuted as terrorism.
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I wonder if this could be argued (119 injured in first Bryansk Oblast attack) - https://en.wikipedia.org/wiki/2025_Russia_bridge_collapses - Russia described the perpetrators as terrorists acting on behalf of Kiev regime.
@dorothydomer This could be argued but a) it's in the context of a war between state actors, b) there are definitions of Europe that could include Russia but in the absence of having specified it beforehand it doesn't count to me, per my unappealable judgement call.
@LukeShadwell Any attack that fits the criteria
My read is that the knife attack doesn't hit the 20 deaths or 100 injuries threshold, but if it had this would have resolved positively.
Ten people were wounded in a stabbing attack on a train in Cambridgeshire, England, on Saturday by two suspects who brutally set upon terrified passengers with huge knives — and anti-terror investigators are probing the incident, according to reports.
@LukeShadwell Ukraine’s Office of the Prosecutor General has registered hundreds of thousands of war crime allegations against Russian personnel, including killings of civilians and other serious international crimes. By January 2025, over 150,000 criminal cases relating to Russian war crimes had been registered under Article 438 of the Ukrainian Criminal Code (violation of laws and customs of war).
Mmh, <https://en.wikipedia.org/wiki/2024_Magdeburg_car_attack> wasn't in the wikipedia list, but would count, so the baserate should be higher.