Someone help me get a grasp of this. Feel like am missing some math principles:
If I have
2018 2019
1 2
3 4
5 6
7 8
Total 16 20
The percentage change in totals for $2019$ is $\left[\dfrac{20}{16}-1\right]$% $= 25$%
Shouldn't this give the same result as calculating the individual change for each row and averaging the sum of these?
That is: $\dfrac{(100 + 33.3 + 20 + 14.3)}4 ?$
No. What is equivalent is if you express each change in terms of the average of the 2018 values. ${1+3+5+7\over 4}={16\over 4}$ So the change is $25\%+25\%+25\%+25\%= 100\%$ of their average. which when averaged is $25\%$