Agriculture remains the largest user of water. In about half the OECD countries, agricultural water use has increased since 2000, driven by expansion in the irrigated area. But compared to agricultural production, the use of irrigation water slightly declined in the OECD overall. Most OECD countries face at least seasonal or local water quantity problems and several have extensive arid or semi-arid regions where w'ater scarcity is a constraint to economic development. In about one-third of OECD countries, freshwater resources are under medium to high stress. The national indicator may conceal unsustainable use in some regions and periods, and high dependence on water from other basins.