You may have heard people say that you do not have to cite your source when the information you include is “common knowledge.” But what is common knowledge?
Broadly speaking, common knowledge refers to information that the average, educated reader would accept as reliable without having to look it up. This includes:
- Information that most people know, such as that water freezes at 0 degrees Celsius or that Sir John A. Macdonald was the first Prime Minister of Canada.
- Information shared by a cultural or national group, such as the names of famous heroes or events in the nation’s history that are remembered and celebrated.
- Knowledge shared by members of a certain field, such as the fact that the necessary condition for diffraction of radiation of wavelength from a crystalline solid is given by Bragg’s law.
However, what may be common knowledge in one culture, nation, academic discipline or peer group may not be common knowledge in another.
How do I determine if the information I am using is common knowledge?
To help you decide whether information can be considered common knowledge, ask yourself:
- Who is my audience?
- What can I assume they already know?
- Will I be asked where I obtained my information?
- A description of the symptoms of Asperger’s Syndrome would need to be cited for a composition in a general writing class but probably not need citation for an audience of graduate students in psychology.
- A reference to the practice of fair value accounting would be understood by a group of economists, but would need citation to an audience of non-experts.
- A statement reporting that 24% of children under the age of 18 live in households headed by single mothers would need to be cited. This is information that would not be known to the average reader, who would want to know where the figure was obtained.
The best advice is: When in doubt, cite your source.
What is not Common Knowledge?
- Datasets generated by you or others.
- Statistics obtained from sources such as the US Census Bureau and the Bureau of Labor Statistics.
- References to studies done by others.
- Reference to specific dates, numbers, or facts the reader would not know unless s/he had done the research.