Critical events create turning points, disrupt individuals' life courses, and affect wellbeing. Periods of life densely populated with critical events may translate into an acute resource drain, affecting long-term wellbeing more strongly than if the same events were sparsely distributed. We investigate how the co-occurrence of critical events and their concentration in time influence life satisfaction in later life. To do so, we construct a novel indicator, the Concentration Index, based not only on the number but also on the time lag between occurrences. Using retrospective information on critical events in family, work, health, and residential trajectories in Switzerland, we show that the higher the concentration in time of critical events is, the stronger their negative long-term relation to wellbeing, net of sociodemographic characteristics, the total number of events ever experienced, and the time since the last event. Furthermore, relevant gender and social origin differences emerged with a stronger negative association with wellbeing among men and respondents from low socioeconomic backgrounds. Our work clearly shows that simply counting the number of events gives only a partial and potentially inaccurate measure of the complexity of the life course and its relationship with quality of life. Not only how many events experienced matter but also the spacing between them.
