Aggregating Subjective Forecasts: Some Empirical Results
AbstractThe impact on forecast accuracy of aggregating the subjective forecasts of up to 13 individuals was examined for five forecast weighting methods---equal weighting, two ex post methods that took advantage of prior information about the individuals' relative accuracy, and two ex ante methods based on objective and subjective assessments of relative accuracy. The individuals were executives, managers and sales personnel employed by Time. Inc., and the variable forecasted was the number of advertising pages sold annually by Time magazine over a 14-year period. The results show that both the average forecast error and the variance of the error decrease as additional individuals' forecasts are included in the aggregate. Only two to five individuals' forecasts must be included to achieve much of the total improvement available from combining all 13 forecasts. Three of the differential weighting methods produced more accurate forecasts than equal weighting, but the magnitude of the improvement was small. Implications for realistic forecasting situations are discussed, as are conditions under which the use of aggregates seems attractive.
Download InfoIf you experience problems downloading a file, check if you have the proper application to view it first. In case of further problems read the IDEAS help page. Note that these files are not on the IDEAS site. Please be patient as the files may be large.
Bibliographic InfoArticle provided by INFORMS in its journal Management Science.
Volume (Year): 31 (1985)
Issue (Month): 12 (December)
You can help add them by filling out this form.
CitEc Project, subscribe to its RSS feed for this item.
- Ramnath, Sundaresh & Rock, Steve & Shane, Philip, 2005. "Value Line and I/B/E/S earnings forecasts," International Journal of Forecasting, Elsevier, vol. 21(1), pages 185-198.
- Hurley, W. J. & Lior, D. U., 2002. "Combining expert judgment: On the performance of trimmed mean vote aggregation procedures in the presence of strategic voting," European Journal of Operational Research, Elsevier, vol. 140(1), pages 142-147, July.
- Osherson, Daniel & Vardi, Moshe Y., 2006. "Aggregating disparate estimates of chance," Games and Economic Behavior, Elsevier, vol. 56(1), pages 148-173, July.
- Ilan Yaniv, 2005. "Receiving Other People's Advice: Influence and Benefit," Discussion Paper Series dp405, The Center for the Study of Rationality, Hebrew University, Jerusalem.
- Fischer, Ilan & Harvey, Nigel, 1999. "Combining forecasts: What information do judges need to outperform the simple average?," International Journal of Forecasting, Elsevier, vol. 15(3), pages 227-246, July.
- Sanders, N. R., 1997. "The impact of task properties feedback on time series judgmental forecasting tasks," Omega, Elsevier, vol. 25(2), pages 135-144, April.
- Scheibehenne, Benjamin & Broder, Arndt, 2007. "Predicting Wimbledon 2005 tennis results by mere player name recognition," International Journal of Forecasting, Elsevier, vol. 23(3), pages 415-426.
- Yaniv, Ilan, 2004. "Receiving other people's advice: Influence and benefit," Organizational Behavior and Human Decision Processes, Elsevier, vol. 93(1), pages 1-13, January.
- JS Armstrong, 2004.
"Forecasting for Environmental Decision Making,"
General Economics and Teaching
- Yaniv, Ilan & Kleinberger, Eli, 2000. "Advice Taking in Decision Making: Egocentric Discounting and Reputation Formation," Organizational Behavior and Human Decision Processes, Elsevier, vol. 83(2), pages 260-281, November.
- Yaniv, Ilan, 1997. "Weighting and Trimming: Heuristics for Aggregating Judgments under Uncertainty," Organizational Behavior and Human Decision Processes, Elsevier, vol. 69(3), pages 237-249, March.
- Lubecke, Thomas H. & Nam, Kyung Doo & Markland, Robert E. & Kwok, Chuck C. Y., 1998. "Combining foreign exchange rate forecasts using neural networks," Global Finance Journal, Elsevier, vol. 9(1), pages 5-27.
- Budescu, David V. & Rantilla, Adrian K. & Yu, Hsiu-Ting & Karelitz, Tzur M., 2003. "The effects of asymmetry among advisors on the aggregation of their opinions," Organizational Behavior and Human Decision Processes, Elsevier, vol. 90(1), pages 178-194, January.
- J. S. Armstrong & R. Brodie, 2005. "Forecasting for Marketing," General Economics and Teaching 0502018, EconWPA.
- Yaniv, Ilan & Milyavsky, Maxim, 2007. "Using advice from multiple sources to revise and improve judgments," Organizational Behavior and Human Decision Processes, Elsevier, vol. 103(1), pages 104-120, May.
For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: (Mirko Janc).
If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.
If references are entirely missing, you can add them using this form.
If the full references list an item that is present in RePEc, but the system did not link to it, you can help with this form.
If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your profile, as there may be some citations waiting for confirmation.
Please note that corrections may take a couple of weeks to filter through the various RePEc services.