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there was a waiting period in 2018 for accounts but a lot of accounts were created then. If i remember the data end of 2017 and first half of 2018 had the most account created on the chain (maybe till the boom of splinterlands).
A lot of accounts were bots as there was good amount of people trying to exploit the bull market of steem those days.

I do feel that there is a good amount of 2018 accounts still active, or maybe it is just that i most people i know here are from those times.