It is rarely accurate to extrapolate beyond the data, unless you know the
correct form of the equation. Your verbal description does not sound like a
polynomial, which necessarily goes to +/- infinity as the independent
variable goes to +/- infinity.

Jerry

"andyfw" wrote:

Does anyone know how to project polynomial growth trends in excel - ie a
growth rate that initially accelerates and then tapers off after a period -
to trend towards an absolute population size (no further growth) after a
further period.