Secondary data are data that was collected by someone else (probably for a different purpose). This second-hand or published information.
Advantages of using Secondary Data
As secondary data is usually available more cheaply. The collection of secondary data is generally significantly quicker and easier (and hence less costly) than collecting the same data ‘from scratch’
Existing data are likely to be available in a more convenient form, digital format example internet.
Using secondary data can give us access to otherwise-unavailable organizations, individuals or locations.
Secondary data allows the researcher to compare data on ‘time base’ i.e. origin of data to current data.
Secondary data is likely to be pre-processed thus eliminating the time-consuming (and hence costly) analysis stage.
Disadvantages of using Secondary Data
The method used to collect secondary data is often unknown to the user of the data (apart from major sources like Census).
The user has little or no knowledge of the processing methods used.
The user rarely has access to the primary data to check again