waterfall chart

Question

Ok, so trying to wrap my head around this math.&nbsp; &nbsp;I understand how the waterfall chart works in Power Bi in terms of adding/subtracting between periods.&nbsp; &nbsp;&nbsp;&nbsp;What I don't get is the math.&nbsp; &nbsp;This chart is measuring the number of product returns we had from one month to the next.&nbsp; &nbsp;Below is what the tool tips say (for the two big red bars).&nbsp;&nbsp;&nbsp;I do not understand the math of why is an absolute change of 36 an increase of 400%, but a change of 31 is only 69% ??&nbsp;The math checks out...I've use a percentage calculator to check it....but my mind has still not wrapped around this yet.&nbsp; &nbsp;Any math folks out there that can explain this?&nbsp; &nbsp; I have to try and explain this waterfall chart to folks that understand it even less than I do...and when I show them this I know I will get questions.&nbsp;&nbsp;&nbsp;Return Item&nbsp; &nbsp;abc&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Return Item&nbsp; &nbsp;abcMay Return Qty&nbsp; &nbsp; &nbsp; 9&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; June Return Qty&nbsp; &nbsp; &nbsp;45June Return Qty&nbsp; &nbsp; &nbsp;45&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;July Return Qty&nbsp; &nbsp; &nbsp; 76Qty Change&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;36&nbsp; (400%)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Qty Change&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;31 (68.9%)&nbsp;&nbsp;&nbsp;

anonymous · Accepted Answer

The maths is correct.&nbsp;&nbsp;If you start with 9, then 9=100% of your starting quantity&nbsp;9+9+9+9 = 100%+100%+100%+100% = 36 = 400% of 9100/9 x 45 = 500% =&nbsp;Therefor, a 400% increase.&nbsp;&nbsp;If you start with 45, then 45 = 100% of your starting quantity&nbsp;100/45&nbsp; x 76 = 168% = Therefor, a 68% increase.&nbsp;&nbsp;&nbsp;Think of it this way,&nbsp;You have 2 apples. Therefore, 100% of the apples that you have = 2. right?&nbsp;Now, you are given 4 more apples. If your original quantity was 2 but now it's 6, you've got three times the apples, therefore, 3 times 100% = 300% . So the change would be 200% (because you started with 100% (300% - 100% = 200%)&nbsp;

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