This section briefly introduces the forecasting methods used by the FORECAST procedure. See textbooks on forecasting and see the section Forecasting Methods for more detailed discussions of forecasting methods.

The FORECAST procedure combines three basic models to fit time series:

• time trend models for long-term, deterministic change

• autoregressive models for short-term fluctuations

• seasonal models for regular seasonal fluctuations

Two approaches to time series modeling and forecasting are time trend models and time series methods.