Membership: Rising or Falling?

Dear all,

I am trying to find out whether number of members of my organisation has a rising trend or a falling trend.

There are several groups of them:
(1) Group A: retention rate = 90%
(2) Group B: retention rate = 60%
(3) Group C: retention rate = 20%

Could anyone how can I find out whether membership (count) is rising or falling??

Thank you in advance.


Less is more. Stay pure. Stay poor.
Yeah, I agree with @Dason that you need to provide greater detail. In addition, 90% could mean 9/10 or 9000/10000, and if not all Groups are the same size - this is important. Also, are these just retention rates for 3 groups for the same period? If everything is the same between group data collection besides the counts and denominators you could be looking at pairwise rate ratios or rate differences, which without denominators can't be calculated with confidence intervals needed to understand power and statistical significance.