Poverty causes malnutrition, but malnutrition also contributes to poverty through increased morbidity, impaired development in children, and reduced capacity for work and productivity in adults. In rich countries food is a relatively small part of household consumption (10–15%). But in poor countries many households (especially those of wage labourers and landless people) use a large share of their income (40% or more) to buy food, so food price rises adversely affect purchasing power by reducing real income. Staples account for most expenditure on food for the poorest people, so increases in price might reduce the amount and quality of food consumed, thus increasing the risk of malnutrition and its consequences.