Delphi effect
The Delphi effect is described by Eric S Raymond in his book, "The Cathedral and the Bazaar" as:
"Sociologists discovered that the averaged opinion of a mass of equally expert or equally ignorant observers is quite a bit more reliable a predictor than the opinion of a single randomly-chosen one of the observers."
Raymond himself believes at least some of the work substantiating this effect was done at RAND Corporation. This may refer to the work on the Delphi Method or Technique described below.
The Delphi effect may also be related to the "delphi pool" concept introduced in the novel "The Shockwave Rider" by John Brunner, which is a work of fiction, and not backed up by scientific research.
Delphi Method or Technique
The "Delphi Effect" appears to be synonymous with the Delphi method. The Delphi method is based on the assumption that group, as opposed to individual, judgement of trends can improve the validity of forecasts. It was developed at RAND Corporation in the early 1950s in a project funded by the US Air Force. It has been used ever since, together with various modifications and reformulations, such as the Imen-Delphi procedure.
A heavily referenced work on this method is:
The Delphi Method: Techniques and Applications, Harold A. Linstone and Murray Turoff, Editors Linstone & Turoff, 1975
which is made available by the editors on the web at:
http://www.is.njit.edu/pubs/delphibook/
it has an extensive biliography at:
http://www.is.njit.edu/pubs/delphibook/appendix.pdf
where the first RAND paper is:
"Sackman, H., Delphi Assessment: Expert Opinion, Forecasting and Group Process, R-1283-PR, April 1974. Brown, Thomas, An Experiment in Probabilistic Forecasting, R-944-ARPA, 1972."
An earlier paper published by RAND is:
Document No: P-3925, 1968, 15 pages
"Delphi Process: A Methodology Used for the Elicitation of Opinions of Experts. ", Bernice B. Brown
available at:
http://www.rand.org/cgi-bin/Abstracts/ordi/getabbydoc.pl?doc=P-3925
A referenced history of the Delphi concept is also available here:
http://www.elthamcollege.vic.edu.au/arthur/delp_2000_history.htm