Forces that move the series toward some mean. An example is a measure of the performance of a professional athlete, such as a batting average; his average for the first three games of the current season would tend to regress toward his historical average. For a new player, his average might regress to the average for new players. Regressing forces are discussed in Armstrong, Adya and Collopy (2001).

• Armstrong, J. S., M. Adya & F. Collopy (2001), “Rule-based forecasting: Using judgment in time-series  extrapolation,” in J. S. Armstrong (ed.), Principles of Forecasting. Norwell, MA: Kluwer Academic Press.