Wages and projection data are not available for every occupation in the system, and which occupations have data can vary from year to year. The information is compiled based on responses to the annual Occupation Employment Survey (OES). This survey is sent to a sample of employers to collect information on wages and employment. In some cases, information on specfic occupations is suppressed and will not be available in the system. Suppression can occur for confidentiality, privacy or statistical errors.