Wikipedia:Citing consensus

It is sometimes necessary to cite consensus in cases where reliable sources may differ, but the overwhelming majority lie on one end of a subject. In such cases it is helpful to establish the consensus viewpoint, even while acknowledging the existence of non-consensus views. This guideline is intended to cover the manner of citing the fact that a state of consensus exists, a process complicated by the necessity for multiple references to secondary sources or tertiary sources.

To truly discover a state of consensus on a matter requires an extensive survey of the subject matter, which can only ever be summarized in a reference footnote. Such a survey, if controversial among editors, should be discussed in depth on the discussion page until a consensus among Wikipedians themselves is reached. Then, a selection from the most reliable of the tertiary sources (preferably three of four sources) should be selected for the reference in the article. Without neglecting opposing points of view in our attempts to present a neutral point of view article in keeping with fundamental Wikipedia principles.

In cases when there is one paramount reliable source (for example, an uncontroversial census as a source for demographic information), then there is no need to establish consensus by citing secondary sources or tertiary sources that are clearly derivative of it. Such over-referencing would only serve to create an inappropriate appearance of "super-consensus".