Demand for Accessories can follow the path of the original equipment and can be highly correlated to the demand of the original item - but there are some subtle factors that can affect the demand planning for such items.
This should not be confused with forecasting for spare parts - as spare parts demand is NOT contingent on the original purchase or ownership of the product but more on the failure or need for a repair of the original product.
The demand pattern can be similar to the Original equipment. Two factors to consider:
1. Attach Rates
2. Time lag from the purchase of the original product
Have any of you calculated attach rates and used this in your forecasting?
Here is an example of smartphones and smartphone cases - near perfect correlation. Some situations can be relatively easy like the smartphone cases or the Apple USB-C brick that has made many consumers irate.
But some can be quite complex and can be inter-generational like the refill brush heads for my Oral-B Power brush from 2002... Happens with a lag and often depends on the number of Original Equipments out there in use.
Learn more on demand models for different scenarios.