In the nps score calculation, only the latest answer of the user is taken into consideration.

For example, if a user gave you score of 10, 3 months ago, he has been regarded as a promoter. Today, if s/he sees the survey again and gives you 8. Now, s/he will be regarded as a neutral.

Check out this article to find where the NPS Data is located:
http://help.userguiding.com/en/articles/3725512-where-are-the-nps-responses-located

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