Here's a simple exercise, or anecdote, to bring up when the subject of NPS (Net Promoter Score) arises:
"Did you hear about the CEO whose company saw these NPS numbers in his customer service groups quarterly reports: 15 in period 1, then it moved up steadily to reach 30 a few periods later. Hooray!" (Right? - Wrong!)
15: 50 (in the top boxes of the "Would you recommend..." scale) minus 35 (in the bottom boxes) = 15. (or was it: 20 minus 5, which also equals 15?)
30: 30 (in the top boxes of the "Would you recommend..." scale) minus 0 (in the bottom boxes) = 30.
(or was it: 50 minus 20? ...or: 60 minus 30? ...or: 65 minus 35?)
What actually (might have) happened is that the unhappy customers left, while the number of those who are the happiest dwindled by 20 percentage points. This may be why such a company could soon go bankrupt (if its competitors are on their toes!)
(Of course, considering the alternative numbers in parentheses above, maybe what happened is that top box responses, i.e., "Recommenders", rose by 15 percentage points, e.g., from 50% to 65%? ...or by 45 percentage points, e.g., from 20% to 65%?).
So, don't tell me your NPS, tell me the shape of your complete "Will/Won't Recommend Curve"!