olemus
(toote, süsteemi, platvormi)
kasutusel olevate eksemplaride koguarv,
pole sama mis müügitulu väljendav turuosa

Wiktionary:
(idiomatic, business) the number of units of a system or product that are currently in use

ülevaateid
https://smallbusiness.chron.com/difference-between-customer-base-installed-customer-base-40268.html

https://en.wikipedia.org/wiki/Installed_base

näiteid
https://duckduckgo.com/?q=installed+base+statistics&t=h_&iar=images&iax=images&ia=images