They are sensitive, however, as absolute poverty measurements are, to within-country price differentials both between regions and across income groups, and how these are taken into account, as well as to the quality of source data on the income distribution. Using the dollar-a-day poverty line as an international standard is an arbitrary choice that focuses attention on the first of the "hierarchy of capabilities". Treating absolutely poor people in the same way as relatively poor people risks drawing attention away from the first capability of overcoming barriers to physical survival, which is the priority in most international efforts to improve the lives of the poorest (World Bank [1990]; Ravallion, Chen, and Sangraula [2008]).