Attach rate

The attach rate of a product represents how many complementary products are sold for each primary product. For example, the average number of DVD discs (complementary product) purchased for each DVD player (primary product) sold, or the number of console-specific video games purchased for each console sold.

The attach rate is one measure of popularity for a given platform, since it is an indication of how quickly sales for the complementary products will grow as the installed base of the platform grows. For example, imagine the following situation:

* Platform A has sold 1,000 hardware units
* Platform B has sold 10,000 hardware units
* Publishers have sold 5,000 titles for Platform A
* Publishers have sold 10,000 titles for Platform B

In absolute terms, Platform B is outselling Platform A by a factor of 10:1, but Platform A has a much higher attach rate (5:1 versus 1:1). Thus for a content provider, Platform A may be more attractive since it only needs to sell another 1,000 units (for a total of 2,000) in order to have the same number of titles as Platform B.

Nevertheless, the attach rate can be skewed early on in a product's lifecycle due to the effect of early adopters whose consumer behavior may not be representative of the general populace. Attach rates also fails when considering observing a product late in its lifecycle. Using the DVD player example above, the adoption of DVD-ROMs in computers and video game consoles and software would have a dramatically negative effect when the complementary product is DVD Videos because many of these multi-use devices rarely are used to play videos.

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