What is the formula for calculating constant percent change?

1 Answer
Alan P.
Sep 13, 2015

For the period from #t_1# to #t_2# for some state #f(t)# with a constant percentage change, that constant percentage change is given by:
#color(white)("XX")(f(t_2)/f(t_1)-1)*100%#

Explanation:

The actual change from #t_1# to #t_2# is
#color(white)("XX")f(t_2)-f(t_1)#

The change as a fraction of its value at #t_1# is
#(f(t_2)-f(t_1))/f(t_1) color(white)("XX")=color(white)("XX") f(t_2)/f(t_1) -1#

or,
as a percentage:
#color(white)("XX")(f(t_2)/f(t_1)-1)*100%#

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