Long-term causal effects of far-right terrorism in New Zealand

Background: the 2019 Christchurch mosque attacks perpetrated by a far-right extremist killed 51 people, yet boosted public acceptance of Muslim minorities. Similar short-term effects have been observed elsewhere.Questions: are these effects durable? And are any such effects evident across the political spectrum?Challenge: identifying long-term causal effects requires estimating unobserved attitudi- nal trajectories without the attacks.Approach: we use six pre-attack waves of Muslim acceptance responses from the New Zealand Attitudes and Values Study to simulate missing counterfactual trajectories (NZAVS cohort 2012, N=4865; replicated in 2013 cohort, N=7,894). Findings: 1) the attacks initially boosted Muslim acceptance; 2) the magnitude of initial Muslim acceptance boost was similar across the political spectrum; 3) No changes were observed in negative control groups; 4) two and three-year effects varied by baseline political orientation: liberal acceptance was stable, conservative acceptance grew relative to the counterfactual trend.Importance: the attacks initially added five years of growth in Muslim acceptance, with no regression to pre-attack levels. Continued growth among conservatives highlights the attack’s failure to divide society. These results demonstrate the utility of combining causal inference with national-scale panel data for answering basic psychological questions of applied interest.