efficiently mobilizing resources could be allowed to squander (within reasonable limits) some of these resources in unwise spending choices. Such an approach, however, would not do justice to the norm of progressive realization embodied in Article 2, para. 1 of the Covenant, which requires that States do everything they can to realize the Covenant rights, both at the collecting and at the spending sides of the equation. We may provisionally conclude that, while the three elements of the equation -- resource mobilization, public spending and outcomes -- are interdependant, they are only imperfect substitutes for one another. Poor resource mobilization is a problem even if the State is highly efficient in using the scarce resources it does manage to mobilize, and inadequate definition of spending priorities is a problem even if the resources available are plentiful and allow the State to meet the basic needs of the population: in both instances indeed, the State could, and therefore should, do more. And where outcomes are achieved in areas such as housing, education or healthcare without much public resources being invested, the results may be considered as fragile, and the risks of discrimination on grounds of wealth and segregation in many cases real: where allocation of scarce goods is left to the market, the poorest may be priced out from access, and even if mechanisms such as subsidies, education vouchers or maximum fees are introduced to reduce that risk, serious problems of accountability towards the public remain. It is within the broad conceptual framework that we can examine its different elements. For the question remains entirely open: how much should States do, and how to measure whether they are doing enough? The following sections attempt to provide an answer. V. Resource mobilization The resources needed for the realization of economic, social and cultural rights may be mobilized both domestically and internationally. The most important sources of domestic revenues include trade tariffs (on imports and on exports), taxation, the royalty fees obtained from companies (both domestic and foreign) exploiting natural resources, as well as fees that may be imposed on the users of public services such as schools or hospitals. States may also seek international assistance and cooperation in meeting their obligations towards the population. Finally, States may benefit from development aid or borrow to finance their policies. Although taking loans may come at the risk of increasing their annual public deficit and, ultimately, their public debt, it may be justified particularly in times of economic downturn and insofar as the debt finances policies that may be seen as investments rather than merely as a stop-gap to meet current expenditures.94 While it would not be possible to review all the possible sources of public revenue in relation to the Covenant, it may be relevant to comment on three sources in particular, due to their specific relationship to the Covenant and to their importance: these are the royalties from the exploitation of natural resources, taxation and request for international support through development assistance or financial loans. They are examined in turn. 1. Exploitation of natural resources As mentioned above, consistent with the right to self-determination, revenues from the exploitation of natural resources (such as minerals, oil and gas, but also agriculture) should benefit the local population.95 But we again must take into consideration the complementarity between resource mobilization and spending : if the local population is to benefit, that presupposes that the royalties are set at a high enough level, allowing to make the appropriate social investments. 94 Rathin Roy and Antoine Heuty (eds), Fiscal Space: Policy options for financing human development (Earthscan and UNDP, New York, 2009). 95 See above, text corresponding to note 38. 22