A factor is a variable that shows the relation of some other variable to the item being forecast. These are historical records of the fluctuations in economic variables. To the extent that some industries exhibit patterns of behavior over time, this tool can be very helpful to marketing managers engaged in strategy planning. This is a kind of time series that changes in the same direction of the series to be forecast, but ahead of it in time. In short, this provides an early warning of what is going to happen in the market before it actually begins.
Indices are statistical combinations of several time series.
Jury of Executive Opinion. One of the oldest forecasting methods, this combines the opinions of experienced executives. Other opinion-based forecasts can be derived from the sales force or from consumer surveys, etc.