comparing 3 percentages want to have a single number to describe the overall change can I use two relative change calcs?

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I am not a math whiz so be gentle please. I want to reduce down the change in 3 percentages to a single value that will allow me to compare other sets of 3 percentages. I am looking at using three relative change calcs to do this. SO percents are A B C and I want to find a value that defines the relationship of A going to B going to C. So reading A would be OLDER than B and B older than C.

 I am using relative change calc  ( new - old)/old) * 100

  D = ((B - A) / A)) * 100 
  E = ((C - B) / B)) * 100 

Here is an example

A       B       C        D = Rel chg A to B      E = Rel chg B to C     Rel chg D to E
66.55   59.68   96.93    34.756                  8.073                  -76.772
67.36   90.68   88.32    34.62                   -2.713                 -107.537

So, remember I am no math whiz, is that the change in the first ABC are slowing LESS than the second group of ABC. Is this mathematically valid OR am I messing up somewhere?