High and volatile food prices can lead to irreversible harm - a loss of physical and long-run human capital, which may reinforce poverty traps through diminished income, resulting in malnutrition, mortality, withdrawal of children from education and a consequent sustained high level of unemployment. A lack of dietary diversification aggravates the problem as price increases in one staple cannot easily be compensated by switching to other foods. First, agricultural output varies from period to period because of natural factors such as weather, disease and pests.