Tom Letcher wrote:
This [Bernie's] method is appropriate for things
(like population and financial investments) that grow
exponentially I believe, is that right? Although some
of my data are financial, they are allocations, so will
not grow [...] in that way.

Your first posting said that you are trying "to
calculate growth", and you previously calculated the total
percentage gain (loss) over many years. That gave the
impression of compounded growth.

In case it helps, this is an example of the type
of data I'm using:
1999-2000 2000-2001 2001-2002 2002-2003 2003-2004
602,510 693,462 802,933 816,473 829,214

It appears that you are saying that the amount allocated
at the beginning of 2000 (693) is unrelated to the amount
at the end of 1999 (510), for example -- other than perhaps
due to policy.

If that is the case, then your original method does seem
incorrect, and your proposal to compute the arithmetic
average of each year's growth rate does seem to be correct.