Since not all unemployment may be "open" and counted by government agencies, official statistics on unemployment may not be accurate. In the United States, for example, the unemployment rate does not take into consideration those individuals who are not actively looking for employment, such as those who are still attending college.According to the OECD, Eurostat, and the US Bureau of Labor Statistics the unemployment rate is the number of unemployed people as a percentage of the labour force. "An unemployed person is defined by Eurostat, according to the guidelines of the International Labour Organization, as:

someone aged 15 to 74 (in Italy, Spain, the United Kingdom, Iceland, Norway: 16 to 74 years);
without work during the reference week;
available to start work within the next two weeks (or has already found a job to start within the next three months);
actively having sought employment at some time during the last four weeks. "The labour force, or workforce, includes both employed (employees and self-employed) and unemployed people but not the economically inactive, such as pre-school children, school children, students and pensioners.The unemployment rate of an individual country is usually calculated and reported on a monthly, quarterly, and yearly basis by the National Agency of Statistics. Organisations like the OECD report statistics for all of its member states.Certain countries provide unemployment compensation for a certain period of time for unemployed citizens who are registered as unemployed at the government employment agency.
Alternatives
Limitations of definition
Some critics believe that current methods of measuring unemployment are inaccurate in terms of the impact of unemployment on people as these methods do not take into account the 1.5% of the available working population incarcerated in US prisons (who may or may not be working while they are incarcerated); those who have lost their jobs and have become discouraged over time from actively looking for work; those who are self-employed or wish to become self-employed, such as tradesmen or building contractors or information technology consultants; those who have retired before the official retirement age but would still like to work (involuntary early retirees); those on disability pensions who do not possess full health but still wish to work in occupations that suitable for their medical conditions; or those who work for payment for as little as one hour per week but would like to work full time.The last people are "involuntary part-time" workers, those who are underemployed, such as a computer programmer who is working in a retail store until he can find a permanent job, involuntary stay-at-home mothers who would prefer to work, and graduate and professional school students who are unable to find worthwhile jobs after they graduated with their bachelors degrees. Internationally, some nations unemployment rates are sometimes muted or appear less severe because of the number of self-employed individuals working in agriculture. Small independent farmers are often considered self-employed and so cannot be unemployed.