The definition of the population of the study varies among the surveys.
Source of information
In several of the surveys analysed, the business owners or
managers, in addition to the workers, are used as a source of information.
With regard to the population and the source of information, there are three different situations:
- Surveys addressed to workers only. This is the most common procedure.
- Surveys addressed to business owners only. Examples are the 'Continuing Vocational Training Survey' and 'The state of occupational health and safety in Hungary' survey.
- Surveys addressed both to employees and employers. These surveys aim at obtaining, with different questionnaires, both the worker's perspective and the company owner or manager's perspective. These surveys were conducted in Canada, Germany, Spain and UK.
Employee and company selection criteria
The variables considered to define the population of the surveys are: occupation or economic activities, company size, employment status, age, and residency. All surveys included both employees and employers.
Economic activity: Although most of the surveys consider all economic activities, some surveys specifically exclude some activities, primarily agriculture, hunting, forestry, fishing, mining or household activities. The Hungarian 'The State of Occupational Health and Safety survey' excludes a large number of economic activities.
Occupation: All surveys did not specifically exclude any occupations. In additional survey in 2005, the Danish Work Environment Cohort Study (DWECS) selected specifically, populations in the following occupations: carpenters, police workers, social workers, taxi and bus drivers, concrete labourers.
Company size: Company size was only mentioned as an inclusion criteria for the 'Workplace Employment Relations Survey' (UK) which includes establishments with 5 or more employees.
Employment status: The surveys usually focus on salaried and self-employed workers. In some cases, it is limited to people who worked during the previous week or who work a certain number of hours (for instance, the Finnish 'Quality of Work Life Survey' (QWLS) is centred on employees whose normal working hours amount to at least five hours). However, some surveys, in addition to active workers, also include other categories in the population under study, such as the unemployed (for example in the Finnish 'Working Life Barometer' unemployed included in some years; the German 'Microcensus' focused on both people in employment and inactive population).
Age: Another criterion which is occasionally included to define the population, particularly in surveys with residence as the sampling unit, is the age of the potential interviewee. The age range considered varies from one survey to another. The lower limits are variously 15 (in some transnational surveys, Austria, Czech Republic, Korea, Netherlands, the Canadian 'Workplace and Employee Survey' and the Finnish 'Quality of Work Life Survey'), 16 (Sweden, United Kingdom and in the 'Working life Barometer in the Baltic Countries' survey), 18 (Denmark, Finnish 'Working Life Barometer', and USA) or 25 ('Continuing Vocational Training Survey', Finnish 'Work and Health Survey'). In some cases, an upper limit is also established, which varies from 59 (Denmark) 64 (Finland, Korea, Netherlands, Sweden), and 69 (Canada, Czech Republic).
Residency: Finally, the definition of the population of many of the studies includes the need for the person to be a resident of the country and to be familiar enough with the country's official language to respond to the interview.