Routine data are data collected continuously or at least repeatedly with some time intervals. They are collected in various ways, e.g., registration by the health services or by interviews with patients or population groups. The data could then be stored and administered in register format. Health registers contain data on persons with diseases or health-related events. The coverage can vary from a total registration to a population sample and from national to regional or local coverage. Data can be routinely collected for various reasons, from economic and administrative purposes to more strict epidemiological purposes.