Trying to understand 100% Stacked charts

[Aaron Bratcher]

Given this data set:
Category Value1 Value2 Value3
January 10 14 15
February 20 24 18
March 14 26 24
April 12 18 28
May 15 12 34
June 17 14 33
July 13 23 27
August 18 25 36
September 15 16 30
October 23 15 34
November 14 22 38
December 11 17 24

When I make a simple 100% stacked line chart, the Value3 data is a
horizontal like at 100%. Is this supposed to be my basis of how the
other value colums are plotted? If so, shouldn't some of them go over
100%? (February has higher values for Value1 and Value2 for instance.)

Or how am I supposed to be looking at what is presented?

Thanks.

 

[Jon Peltier]

Aaron -

The 100% refers to each category; the values are normalized to the total
for each category (each month in your example). For January, Value 1 is
plotted at 10/39 or 25.6%, value 2 at (10+14)/39 or 61.5%, and value 3
at (10+14+15)/39 or 100%.

- Jon