Long-term unemployment refers to people who have been unemployed for 12 months or more. The long-term unemployment rate shows the proportion of these long-term unemployed among all unemployed. Unemployment is usually measured by national labour force surveys and refers to people reporting that they have worked in gainful employment for less than one hour in the previous week, who are available for work and who have sought employment in the past four weeks. Long-term unemployment causes significant mental and material stress for those affected and their families. It is also of particular concern for policy makers, as high rates of long-term unemployment indicate that labour markets are operating inefficiently. This indicator is measured as a percentage of unemployed.