Why is measuring percent change (or Year over year change) of percents bad? So I'm calculating female representation of our workforce and trying to track changes over time. So say in Jan 2018 I had 40% of the workforce are females and in Jan 2019 I had 45%. The percent change is 12.5%. I'm getting push back on this because "calculating percent change of percents is bad". However, if I was to calculate percent change on the actual number of females let's say 100 in Jan 2018, and 200 in Jan 2019, it would seem like our female representation should have doubled, but in reality the business grew. So by taking the percent change of percents, I feel like I'm accounting for any major fluctuations in headcount movement. 
What am I missing here?
 A: Hello and welcome to math.stackexchange. 
First off, a narrative accompanying a numerical report (as in your post) is always good. Our XYZ grew from 40% to 45% because blablabla is better than Our XYZ grew from 40% to 45%. But a percentage change of a percentage can be downright misleading. Our XYZ percentage grew by 100% is misleading when in fact Our XYZ grew from 1 (in 50) to 2. 
There are other ways to be misleading about percentages: 95% fat free is the same as contains 5% fat, but it sounds better and therefore is misleading.
In some cases it may be OK to report a percentage change of a rate, but then it should be accompanied by information about the actual rates: The frequency of work accidents fell from 3 per 100,000 person hours to 2 per 100,000 person hours, which is a 33% decline in the accident rate.
A: Don't calculate the percentage change of the percentage, or the percentage change of the absolute, calculate the absolute change of the percentage.
So, if last year you had 40%, and this year you have 45%, the important number is 45% - 40% = 5%.
