An individual-based approach to the measurement of multiple-period mobility for nominal and ordinal variables

This paper discusses meanings of intra-generational mobility when variables take values corresponding to either unordered or ordered categories. We propose concepts of maximum and minimum mobility, along with mobility-inducing transformations and related desirable properties. Then we axiomatically characterize indices of individual mobility and social mobility. Our first set of concepts, properties and indices, measures mobility as diversity, unpredictability or instability in people’s status along the accounting period. This notion of mobility is relevant and applicable to both nominal and ordinal variables. Our second set measures mobility as average distance traveled across categories from one period to the next. This latter notion is only relevant for ordinal variables. We apply these indices to measure the extent of mobility in the responses to subjective wellbeing questions in the United Kingdom, using the British Household Panel Survey.