How to graph change as a percentage of volume in Excel?

Bad title, but this is what I’m trying to do. I’m trying to compare changes in production between two departments over the course of a year. The problem is one department is much bigger than the other and handles a lot more volume.

So, lets say Department A makes 1000 widgets in March and 1400 widgets in April.
Department B makes 100 widgets in March and 300 widgets in April.

Just a line graph showing the change in numbers does really tell the story, because while Department A increased production by 100 more widgets than Department B, it was only a 40% increase vs. a 200% increase for Department B.

I’d be inclined to calculate the two deltas (department x month-to-month change), convert them to percentages of overall volume (the first value), and the graph those on a 0-to-100 (or negative if needed) percentile Y-axis.

I’d think that a line graph showing production by month, with one line for each department, would do quite well. You’d see that B’s line is still far lower than A’s, and that immediately draws the eye to the relatively stark uptick from March to April.

Don’t try to graph the change, 40% increase or 200% increase. Just graph the production, and people looking at it will be able to see the changes. That’s my opinion anyway.

You have two choices -
graph percents; or have a hidden column that converts one baseline (100 widgets/month) to the other (1000/month)
That of course brings in the problem “how to label axis”?)
Convert them both to a common baseline (i.e. divide by 100, divide by 1000) in a pair of hidden columns, graph that.
Label the axis “production” and it will show 1,2,3,4,5…
The text label would be : “Production - Dept A, -1,000’s, dept B -100’s” )

This allows people to read the graph and figure out production amounts, while percent really doesn’t give that detail.

Of course if the base amounts are not nice neat multiples, the graphs won’t start at the same number.
Let’s say, A produced 1150 widgets in January, B produced 217 - A will start at 1.15, Bat 2.17 - but the graphs will be in the same rough (comparable) scale.