approach, countries such as Moldova, Malawi and Tanzania, though scoring low on the HDI, would score well on the SERF Index (Social and Economic Rights Fulfilment Index, initially referred to as the "Economic and Social Rights Fulfilment Index - ESRF Index"); the reverse would be true for Mexico and Malaysia, two countries which, although relatively well ranked on the HDI, could do much better to fulfil economic and social rights given the resources at their disposal.204 Alternatively, in another, slightly different version of the same approach, the degree of fulfilment of the right (z) could be assessed as a value between 0 and 1, calculated as the ratio between the actual achievement of the country (x) and the maximum level of achievement possible at the per capita income level of the country concerned, such a maximum being based on the highest level of the indicator historically achieved by any country at that per capita GDP level (y). This latter approach is called the "Achievement Possibilities Frontier Approach", a terminology that adequately conveys that it seeks to assess a country's performance against the best performing country at the same level of development, as indicated by the GDP per capita.205 Its main advantage, the authors note, lies in the "theoretical coherency of assessing a country’s fulfillment of its obligation of progressive realization based on the level at which a country with a given per capita GDP could perform".206 The APF approach does not differ in fundamental ways from a proposal made in 2007 by Cingranelli and Richards that we adopt as a standard (in order to assess the performance of any particular government in implementing economic and social rights) "whether the condition of the poorest people in a country is better or worse than the condition of the poorest people in other countries that are peer benchmarks, because the available wealth per capita is similar".207 The major difference, evidently, is that whereas the APF approach provides a relatively stable baseline (as it is based on historical precedent), the Cingranelli-Richards standard is constantly shifting, based as it is on the changing average performance of the peers, which makes comparisons across time more difficult: even a country making significant progress could be scoring less well if the other countries at the same stage of development move forward even faster. The approach developed by Sakiko Fukuda-Parr and her colleagues, now systematically exposed in a book-length publication,208 provides an elegant way to distinguish between how a State performs on human development indicators, and how it performs on indicators of economic and social rights fulfilment: indeed, to rank countries on this second metrics, we must distinguish between a country's unwillingness to do more to support economic and social rights and its inability to do so, and that is what the definition of an "achievement possibility frontier" should help to achieve. At the same time, the demarche of Fukuda-Parr and her colleagues is incomplete. The method of analysis per definition cannot integrate the duty of the State to seek international support, when the domestic resources that could be mobilized are insufficient.209 Perhaps more fundamentally, the method proposed confronts us with the question of how the capacity of a State to fulfil economic and social rights should be measured. Such capacity is determined essentially by reference to the GDP per index based on indicators of infant mortality, life expectancy at age one, and adult literacy rate -- under the auspices of the Overseas Development Council in the late 1970s (see David Morris, Measuring the Condition of the World's Poor: The Physical Quality of Life Index (New York: Pergamon, 1979)). Moreover, separate index scores would be developed for lowand middle-income countries on the one hand, and high-income countries on the other hand, to take into account the very different situations of these respective groups of countries. 204 Id., at 31. 205 Id., at 18. 206 Id., at 20. 207 David Cingranelli and David Richards, "Measuring Government Effort to Respect Economic and Social Human Rights: A Peer Benchmark", in Hertel and Minkler (eds), Economic Rights. Conceptual, Measurement, and Policy Issues, cited above note 46, 214-232, at 223. 208 Sakiko Fukuda-Parr, Terra-Eve Lawson Remer and S. Randolph, Fulfilling Social and Economic Rights (New York, Oxford Univ. Press, 2015). 209 The deliberate choice to exclude foreign aid from the count of available resources for the purposes of constructing the SERF Index is justified by the authors by a lack of reliable data, by the weakness of the evidence concerning the effectiveness of aid, and finally by the fact that "the resources at a country's disposal from the international community are in part a reflection of the country's policy choices" (Fukuda-Parr et al., Fulfilling Social and Economic Rights, cited above note 208, at 54-55). These seem rather weak justifications for this methodological choice. 44