Is that common terminology? It sounds like you're defining "growth rate" as "exponential growth rate." To me, if you're seeing 10, 15, 20, 25, etc. every month, then your monthly growth rate is a constant 5. You're still growing, it's just that your growth every month isn't a function of your size last month.

... whereas if your downloads per time month is a constant proportion of your total downloads to date, e.g., next month the downloads will total 2.5% of the total downloads to date ... and that keeps happening every month, then:

  * the per-month downloads will grow exponentially as you graph it over time
  * the cumulate number of downloads to any given date also will grow exponentially

Ok, I understand now, thanks :).