first for financial sustainability to be respected a nonmarginal number of users will have to pay more than the longterm average cost of service provision a second key aspect is the capacity of the structure to appropriately target the poor defined by komives et al this tariff structure does not qualify as a social tariff as it has not been established that poor households consume much less water than more welloff ones empirical research tends to indicate that income elasticity of water demand is low in other terms the poor do not necessarily consume less water than the rich