Secondary research is a method that reuses existing data that was collected for another project, often by another researcher. This is a relatively inexpensive form of data collection since the costs associated with administering surveys or other instruments have already been conducted. It can also be conducted more quickly and with less manpower than primary data collection. Secondary research is used in many disciplines, including market, medical and social policy research.
There are some advantages to using secondary research as a data collection method over primary research. Secondary research may be used as a starting point for a research project. Before a researcher conducts her own data collection, she may analyze existing data on the topic. This helps tune the research hypothesis and questions. Time and cost savings also make this a valuable research tool. Secondary research helps the researcher avoid some of the pitfalls and challenges of primary data collection activities such as gaining access to a study population or difficulties with administration.
This research method also has some disadvantages. If the original data collection tool was a survey, the original instrument may have asked questions in a way that is inappropriate to secondary analysis or may have collected responses in a manner that can't be properly analyzed. The data sets used for secondary analysis may be out-of-date, which makes them inappropriate for the current research project. For example, a researcher could not write a paper about today's political climate by using data collected in 1980. Also, the original research may not have been conducted rigorously and may have uncontrolled biases.
Many public agencies collect data regularly that can be used for secondary research. The United States Census Bureau provides social and population data of the entire country every ten years with interim data collection in non-census years. The Federal Bureau of Investigation (FBI) collects information regarding crimes and punishment annually. Other agencies such as the Food and Drug Administration (FDA), Department of Labor Statistics, and Bureau of Land Management collect data respective to the populations they serve. This data is available for free use or for a nominal fee.
Private companies and universities are also considered good sources of existing data for secondary research. The Pew Research Center and Gallop® are companies that collect and sell public opinion data. Many university professors collect data for research projects and may make their data sets available for secondary research. This data can be free or very expensive depending on the size of the data set and the source.