Why would it not be linear?
Question is impossible, because it is linear.
https://forum.cryptonote.org/viewtopic.php?f=2&t=10The blockchain size according to a dev is, is linear and 2-3x larger then Bitcoin's own. Thereby being scalable in the same way as Bitcoin is. Because anonymity is the main consideration here and transfers cannot be proven in as much detail as with Bitcoin, blockchain pruning could be a great solution to slim down cryptonote based blockchains in time.