sales different of this year compare to last year in %

[lezawang]

Hi
I am watching a video on how to insert a variant chart (showing negative and positive). The author used the table below. The formula she used to find the difference is

=(B2-C2)/C2

Why is that? why not

=(B2-C2)/B2

Thanks a lot.

company name	sales	sales-previous year	different
company1	600	795	-25%
company2	845	812	4%
company3	841	797	6%
company4	362	441	-18%
company5	349	492	-29%

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[KolGuyXcel]

Usually the "formula" to calculate any "change" is

(present - previous)/previous.