## Overview

Seasonal factors measure the average ratio of monthly data to the corresponding underlying trend value. They are important in the following areas:

- Adjustment of historical data before the fitting of trend models
- Calculation of monthly forecasts corresponding to projected trend values
- Re-phasing of existing monthly forecasts

Seasonal factors may be maintained by

- Using statistical analysis of historical actual demand data
- Manual editing via Edit Seasonal Factors

Seasonal factor codes may be created for any combination of items at any level of detail.

## Estimating Seasonal Factors

- From
**IFP Home**select**Forecasting > Seasonal Factors Estimation** - Select the actual demand data that you wish to use for calculation of seasonal factors. This should include at least two years.
- Select Item Type 01 (
**Sales),**seasonal factors estimation should**not**include the effects of sample movements or free goods - You are advised to set the
**Level of Detail**to the variable that best defines each product (normally product group/brand) as products belonging to the same brand tend to have similar seasonal patterns. - The Seasonal Factors Estimation dashboard will then open.

## Editing a Set of Seasonal Factors

- Select the item that you wish to update. You may edit the default code if you wish.
- Set the required
**Estimation Method**. - Select the period to be used.
- Click
**Re-Estimate.**This will then update the seasonal factors based on the new selections made. - Seasonal factors can then be manually edited using the Seasonal Factors Editor. Note that:
- Calculated factors may be edited to reflect expert opinion
- The average seasonal factor over the year must be 1.0
- Months with higher than average demand have a factor greater than 1
- Seasonal factors are also translated into an equivalent index and as a % of overall total annual demand.
- When you are happy with these changes they can be stored using the
**Save button**on the toolbar.

**Note**: If changes are made to more than one item then click **Re-Estimate All** and **Save All**.

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