Traditional measures of poverty persistence, such as “poverty rate” or the “persistent-risk-of-poverty rate”, do not devote enough attention to the sequence of poverty spells. In particular, they do not put enough attention in underlining the different effects associated with occasional single spells of poverty and the consecutive years of poverty. In this paper we propose a new index which measures the severity of poverty in a longitudinal view, taking into account the way poverty and non-poverty spells follow one another along individual life courses. The index is normalized and increases with the number of consecutive years in poverty along the individual poverty profile. The index is supported by a conceptual framework and characterised via properties and axioms. It is validated and tested on a sample drawn from young European adults participating in ECHP survey.