The attach rate is a concept used broadly in business, especially in marketing, to represent the number of units of a secondary product/service sold as a direct or implied consequence of the sale of a primary product/service. It is often expressed as a sales ratio of primary to secondary units, or as secondary units sold as a percent of primary. The secondary good/service may be an integral component of the primary purchase (e.g., Bluetooth circuits/capabilities sold within electronic devices) or it may require a further consumer decision (e.g., as in video games sold per unit of the primary console sold). For the latter, the association between the primary and secondary may be general and loose (e.g., DVD-Video discs purchased per primary DVD player sold), or may be the result of product-specific designs (e.g., as with console-specific video games, or sales of phone-specific accessories per unit of a particular mobile phone sold).
The attach rate concept is widely used as a means of reporting desirable sales associations/outcomes in the computer/video gaming industry, and in technology-related marketing in general. While complexities of real situations can obscure interpretation, attach rates often provide a metric for marketers of both primary and secondary products, allowing them to assess and even forecast the impact of the popularity of a given technology platform. Rapid sales of primary products create the market for the secondary product; conversely, the sale of platform-specific secondary products provides an indication of longer term demand for the primary platform. Real interpretive complications in technology include the general rapid evolution of both primary and secondary products, as well as factors such as changes to attach rates over a product's life cycle (e.g., because of the unrepresentative behavior of early adopters). Attach rates for products are also used more broadly in marketing, and strategically, attach rates can factor into the decision of a primary product manufacturer to merge with or acquire a secondary product manufacturer, and in the valuation of businesses in such times of times of mergers and acquisitions.