Overall, the OECD average water application rate per irrigated hectare decreased by 7% between the periods 1990-92 and 2002-04, while in most cases the volume of agricultural production increased (OECD, 2010b). This may induce water stress. Some states in the United States, such as California, as well as many Mediterranean countries, already battle with increasing water stress (OECD, 2010b). Figure B.2 provides more detail about the level of water stress in a selection of OECD countries. Although water stress by itself may have negative consequences for productivity, combined with a supporting set of policies it may stimulate more efficient water allocation and the adoption of sustainable water management techniques. However, OECD research (2010) shows that in many countries, farmers are only charged for the operation and maintenance portions of their water supply costs, with little recovery of the capital costs of water supply infrastructure.