Period Options in Statistical Forecasting

You must select the period of historical data used to estimate the trend for each item.

• This period is selected by specifying the first and last year/month
• The default last year and month are the current year and month from the database environment settings.
• The historical period selected here must lie within the selected years of actual/forecast files.
• Any period of at least 6 months of historical data may be used in the estimation of the underlying trend
• For user-defined trend models this restriction is not imposed

Care should be taken when selecting this period for any given item, as an inappropriate choice could lead to unsatisfactory forecasts.

• In general, the longer the period used, the more reliable the estimate of current and future trends
• You should avoid selecting periods containing historical patterns not relevant to the estimation of likely future trends
• Avoid selecting periods including pre-launch months or periods including dramatic changes in the direction of the trend
• A warning will be displayed if the selected period includes 5 or more zero values

Last Actuals Month

The default last actuals month is set to the current month setting for the database (see Database Manager > Environment Settings).

You may override this default setting via the option 'Last Actuals Month'. This is useful where the historical data being used is from a source that is available at a later date that internal actual sales data (e.g. in-market data provided from an external source).

Fixed Periods

An alternative method for selecting the period to be used is to select the Fixed period option. For this option you will need to specify a number of months to be used.  The last year/month will be set to the current year/month and the first year/month will be automatically calculated. For example,  if the number of months is set to 24 and the current month is April, 2014 then the first month will be set to May 2012.