The chart on the site below shows JK Rowling's net worth growth was pretty much linear. $100M per two years until about 2006, then $100M a year after that.

She also pays full UK tax on her earnings, the 36th most of any individual.

https://moneynation.com/jk-rowling-net-worth/

But that's not a response to my question.

It is in the context of this thread, because the article is about exponential growth.