How to make an area chart in Numbers?

A bar chart is a Category chart.

The y axis data is numerical and the bar heights are proportional to those values.

The x axis 'data' is a simply a list of categories to be compared. each category is assigned the same amount of space on that axis.

"I imagine i could make a table with a row for each month and the current rate but that seems like a lot of work for something simple given the monthly rate only changes every so often."

For the type of display you want, that is probably the best process. Here's a Bar chart made following that process.

Same chart with the 'dates' on which no change in rates occurred deleted from the table:

The key to making the 'bars' width match the number of months between rate changes is to remove the gaps between the actual bars, done by setting the gap to 0% in the Chart Inspector:

For more information regarding charts, Take a look at the Charting Basics template, supplied with Numbers.

Regards,

Barry

I do not know of a chart that will do what you want. You can do a line that would be equivalent to the top of your bars but I do not know of a way to fill in below the line.

Scatter chart based on the table shown. I turned on connecting lines and turned off data point symbols. You should be able to create a table like this from your data using formulas.