I asked aquestion on 26 Dec about modelling growth rates and got a very
helpful reply from Herbert Seidenberg (Thank-you), but in trying to apply the
suggested formula there is clearly something I have not fully understood.

I am trying to model growth of service subscribers where the
parameters/variables a

* Ultimate projected number of subscribers (eg 500 members, 560 members...)
* Time to reach Ultimate subscriber numbers (eg 9months, 14months,
20months...)
* Maximum number of net new signups a month (eg 50 members, 70 members...)
* Month in which max new signups achieved (eg month 5, month 7...)

I want to be able to model the growth of the total subscriber-base for
scenarios whe
1) The number of months for the subscriber-base to plateau at a given level
is variable
2) The maximum number of net new subscribers achieved in a month and the
month that is achieved (eg 70 net new in month 7) is variable
3) The rate of net new signups is increasing up to the month of maximum net
new subscribers and declining thereafter (ie an s-curve) and trending to zero
growth/steady state at the end of the defined growth period.

I need to be able to model the net new signups each month for say:

Total subscriber base when mature = 560
Months to build to maturity = 14
Maximum New sign-ups in month = 70 in month 5 (maximum could be expressed as
a multiplier of the average -ie 1.75*40 = 70).

Any further help that can be offered will be much appreciated.