Weekly Fluctuations in Risk Tolerance and Voting Behaviour

Risk tolerance is fundamental to decision-making and behaviour. Here we show that individuals’ tolerance of risk follows a weekly cycle. We observed this cycle directly in a behavioural experiment using the Balloon Analogue Risk Task (Lejuez et al., 2002; Study 1). We also observed it indirectly via voting intentions, gathered from 81,564 responses across 70 opinion polls ahead of the Scottish Independence Referendum of 2014 (Study 2) and 149,064 responses across 77 opinion polls ahead of the United Kingdom European Union membership referendum of 2016 (Study 3). In all three studies, risk-tolerance decreased from Monday to Thursday before returning to a higher level on Friday. This pattern is politically significant because UK elections and referendums are traditionally held on a Thursday—the lowest point for risk tolerance. In particular, it raises the possibility that voting outcomes in the UK could be systematically risk-averse. In line with our analysis, the actual proportion of Yes votes in the Scottish Independence Referendum was 4% lower than forecast. Taken together, our findings reveal that the seven-day weekly cycle may have unexpected consequences for human decision-making. They also suggest that the day on which a vote is held could determine its outcome.