Vulnerability to individual and aggregate poverty

We propose families of measures for vulnerability to both individual and aggregate poverty. We view vulnerability as the burden caused by the threat of poverty. Exposure to states of the world where hardship may strike causes distress ex-ante, even if ex-post the dice are benign and poverty (consumption below a critical norm) does not materialise. We ensure our measures meet a set of desirable axioms—in the case of aggregate vulnerability, this set includes sensitivity to the degree of correlation of outcomes across individuals. We argue that individual vulnerability levels are not enough to compose the aggregate picture, e.g. because society may be wary of the threat of simultaneous, widespread poverty. We illustrate with data from Ethiopia, where rainfall risks are found to raise vulnerability to poverty despite sustained increases in consumption.