This document discusses secondary data, which is data that was originally collected for a purpose other than the current research purpose. There are two main types of secondary data: documents and records, and surveys. Surveys include censuses that collect data on topics like population, employment, and agriculture, as well as regular and occasional surveys on price indexes, family income, labor markets, and more. Secondary data can be gathered and analyzed more quickly than primary data, but may lack accuracy or standard classification and not be appropriate for solving certain problems.