Prospect theory is among the most influential frameworks in behavioural science, specifically in research on decision-making under risk. Kahneman and Tversky's 1979 study tested financial choices under risk, concluding that such judgements deviate significantly from the assumptions of expected utility theory, which had remarkable impacts on science, policy and industry. Though substantial evidence supports prospect theory, many presumed canonical theories have drawn scrutiny for recent replication failures. In response, we directly test the original methods in a multinational study (n = 4,098 participants, 19 countries, 13 languages), adjusting only for current and local currencies while requiring all participants to respond to all items. T...