Share of Shelf (SOS)

Share of Shelf (share of space, SOS, SoS) is an indicator of how much space your products take in relation to all the products. It is measured in percents.

Face is a unit of goods that the buyer sees. If:

• The product is in the first row - it is considered to be a Face. Goods that stand behind it are not considered Faces;
• There is no product in the first row of the shelf, then the product in the depth of the shelf can be considered a Face, provided that it is not covered by anything, and is clearly visible to the buyer;
• The goods on the shelf are in packaging, then all packages are considered one face. For example, a box of chewing gum, a box of loose sweets, or a pack of drinks.

Face on the shelf. This is the Face located directly on the shelf. Faces that are located on other Faces are called stacks.

General formula for calculating shelf share

All goods

Depending on what «all products» mean in the formula for calculating the Share of Shelf, the following are determined:

• Share of Shelf in a category;
• Share of Shelf in relation to key competitors.

Share of Shelf in a category

The numerator of the formula takes into account the place occupied by your products within a certain product category. The denominator is a place occupied by all products within the same product category.

The list of product categories in the project, their boundaries, as well as the signs or groups of products that are included, or excluded, from the product category, are determined at the stage of preparing the product catalog for recognition.

For the correct calculation of the shelf share in a category, all products must be correctly classified by product categories. This should be done for your own products, as well as for regional and local competitors' products.

Share of Shelf in relation to key competitors

The numerator of the formula takes into account the place occupied by your products within a certain product category. The denominator is the place occupied by products of certain brands or manufacturers in the same product category.

The lists of key competitors are set separately for each product category in the project.

With this calculation, the shelf share is less of a subject to uncertainties associated with the definition of the Unknown (not in the catalog) categories of goods and brands.

Space occupied by goods

Depending on what “space occupied by goods” means, the shelf share is subdivided into:

• Share of Faces;
• Weighted share of Faces;
• Share of Faces on the shelf;
• Linear portion of the shelf;
• Area portion of the shelf.

Share of Faces

This is the most basic option for determining the proportion of the shelf. In its pure form, it is almost never used in practice.

The total number of Faces is taken as the space occupied by goods. The distinction between Faces on the shelf and Faces on other Faces is not made, as they give the same contribution to the Share of Shelf. Also, no distinction is made between large and small Faces, as each one of them contributes equally to the numerator or denominator of the formula.

Weighted Share of Faces

This is a complicated version of the Share of Faces. Each SKU is assigned a certain fixed weight. The numerator and denominator in the formula are calculated taking into account the weight of each Face. Face weights can be whole or fractional numbers, either greater or less than one. If the Face weight for the SKU is not specified, then a weight equal to one is used.

Face weights are used for multipacks, clusters, boxes, and other forms of packaging individual items on a shelf.

Share of Faces on a shelf

This is one of the most common methods for calculating a Share of Shelf .

The total number of Faces on the shelf is used as a measure of the space occupied by the goods. Faces that are stacked on other Faces do not contribute to the numerator and denominator of the formula.

Linear Share of Shelf

This is another common method for calculating a Share of Shelf.

The total horizontal size (in millimeters) of all the Faces on the shelf is used as a measure of a space occupied by goods.

For products (your own products and key products of competitors), the size value from the catalog is used, taking into account the orientation of the face (which of its sides is located horizontally). For other products, dimensions in millimeters are estimated, based on pixel dimensions and [photograph scaling](#principles-of-determining-the scale-of-a-photograph).

Area Share of Shelf

The area Share of Shelf is used for goods that are in horizontal refrigerators - ice cream, frozen foods and others.

The total area of all Faces in square millimeters is used as a measure of the place occupied by goods. At the same time, all Faces are taken into account, not just the Faces on the shelf.

Face area is calculated as the product length times width in mm (since the faces are approximated by the rectangles). The sizes themselves are estimated in the same way as the sizes of goods for calculating the linear portion of the shelf.

Principles of determining the scale of a photograph

Photo scale = linear size of the object in the photo in pixels/true linear size of the object in millimeters

The scale of the photo is used when calculating the linear and areal Share of Shelf. It depends on:

• The distance from which the photo was taken;
• Camera lens parameters;
• Parameters of the photo perspective.

The scale of the photograph is estimated based on the observed pixel dimensions in the photograph of objects, for which their dimensions in millimeters are known. These can be well-known products, regular price tags, and others.

If there are several photographs in the scene, then for each one of them its own scale is assessed. In case the photos are overlapping, information from the panorama stitching module is used.

Principles of calculating a Share of Shelf from multiple photos

If one Face appears on several photos in the scene according to the panorama stitching module, it is considered a duplicate. When calculating the shelf share, such Faces are taken into account once, regardless of the method used.

Why are there so many different types of Shares of Shelf, and how do I choose the right one?

The method for calculating the Share of Shelf, based on the results of image recognition, is selected the way so it matches as closely as possible the Share of Shelf manual measurement method adopted by the company. This makes it easy to use the company's historical manual measurements, and it also makes it easy to set Share of Shelf target values.

If the goal is not to match the manual method, it is recommended to use the Linear Share of Shelf in relation to key competitors calculation for all products, except for the ice cream. For the latter, it is better to use the Area Share of Shelf in relation to key competitors. These indicators are the least affected by recognition errors.

Notes

You can order a revision of the method for calculating the Share of Shelf according to your method.

If you have any questions, or experience any issues, please contact our technical support team.