How do I take seasonality out of sales results? I have sales figures and a seasonality curve. ?

Question

I have sales results by month, and a seasonality curve by month for the year. I'd like to spread the results evenly across the year, but am not sure how to do so.

Here is an example - I tried dividing the sales result (original) by the seasonality value for that month, and then dividing the result by 12. The total result is higher than the original total. (Sorry for the poor formatting, not a lot of options here that I'm aware of).

Seasonality Curve Original Adjusted

January 9.0% 100 93

February 7.0% 110 131

March 7.0% 90 107

April 8.0% 60 63

May 9.0% 70 65

June 9.0% 40 37

July 10.0% 100 83

August 6.0% 140 194

September 9.0% 130 120

October 10.0% 160 133

November 7.0% 90 107

December 9.0% 100 93

Total 100% 1,190 1,226

103.0% difference

Answer 1

Sorry -- I should have looked at this closer . I assumed it was more work than it is. (One normally has to calculate monthly seasonality indices.)

The "seasonality curve" numbers you've given are just monthly percentages of annual sales. All you have to do is multiply each monthly proportion by the total sales for the year.

So January is 1190 x .09 = 107; February is 1190 x .07 = 83, annd so on.