A structure evaluation of information previously collected by local,
state, or national agencies is undertaken. Existing sources of health
data (statistics, tracking records, treatment patterns) may be available
on the World Wide Web or through government agencies, local or university
libraries, health departments, clinics or hospitals, police departments,
schools, research or nonprofit organizations.
Organizations may collect data that is not originally intended as health
data, but is useful nonetheless. Examples include grocery store receipts
and even school attendance records. Analysis of existing data is useful
for monitoring and evaluation.