Personality is the strongest and most consistent cross-sectional predictor of high subjective well-being. Less predictive economic factors, such as higher income or improved job status, are often the focus of applied subjective well-being research due to a perception that they can change whereas personality cannot. As such there has been limited investigation into personality change and how such changes might bring about higher well-being. In a longitudinal analysis of 8625 individuals we examine Big Five personality measures at two time points to determine whether an individual's personality changes and also the extent to which such changes in personality can predict changes in life satisfaction. We find that personality changes at least as much as economic factors and relates much more strongly to changes in life satisfaction. Our results therefore suggest that personality can change and that such change is important and meaningful. Our findings may help inform policy debate over how best to help individuals and nations improve their well-being.