Reference lines can add a nice final touch to your visualization. They indicate a key value in your chart, with either a vertical or horizontal line.
Simply click on the analytics tab, and have the line span each pane of sheet 1.
In each pane, we'll calculate the average profit sum across all years.
We'll add a Custom label, which displays information to the viewer in the following format: $<Value>: <Computation> of <Field Name>.
There, this adds a nice touch to our plot! The positioning of the line effectively conveys to the viewer that overall, technology is far more profitable than other categories.