Aftermarket in economic literature refers to a secondary market for the goods and services that are complementary or related to the primary market goods, also known as original equipment). In many industries, the primary market consists of durable goods, whereas the aftermarket consists of consumable or non-durable products or services.

In the moment, aftermarket goods mainly include products and services for replacement parts, upgrade, maintenance and enhancement.

There are two essential elements of the aftermarket: installed base and vendor lock-in effect.

A certain level of installed base of original equipment customers is necessary for the sufficient demand of aftermarket products.

Therefore, significant installed base normally makes aftermarket profitable as an established installed base is likely to consume the aftermarket products repeatedly over the lifespan of their durable goods.

Lock-in effect or installed-base opportunism refers to the situation where the customers can only purchase the aftermarket goods produced by original equipment manufacturer.

The reasons for a lock-in can be:

These two essentials, installed base and lock-in effect, make aftermarket less volatile relative to primary market and therefore more likely to be profitable.