676 HUMAN RIGHTS QUARTERLY Vol. 39 Figure 1. Signaling social rights compliance The standards against which duty-bearers can be measured are provided by the obligation frontier in Figure 1. For example, it is expected that for a duty-bearer with a maximum available resources level of a1, attainment of the welfare basket should be at level m1: duty-bearer a1 has an unconditional obligation to fulfill m1 level of the welfare basket. Therefore, provision of the welfare basket at any point below the frontier, such as m-1, might tell us something about a duty-bearer’s unwillingness to use its maximum available resources to provide for social welfare and could signal a violation of social rights. It might also shed light on the degree to which these rights are being violated: that is, the distance between the observed level of welfare basket attained and the level set by the obligation frontier, in this example: m-1/(m-1 + m1). C. Empirical Strategy Essentially, there are two main methodologies for measuring efficiency: the mathematical (non-parametric) approach, and the econometric (parametric) approach. The two techniques have both virtues and limitations in their respective bids to envelop data, and there is no prescriptive rulebook for