Add average of past years to plot of current year

Hi,

My boss asked me to make some graphs with data of our operating ratio (%) .
It should contain the a value for every month of this year and a value for every past year.
The issue i get is that only the last 20% of the graph is really of importance since this contains the data of the current year.
The first 80% is only 1 point per year and is older data.
I've been trying to fix this but i can't find any documentation about it.

Anyone who can give me a tip about this?

I attached an example of the graph.
The data is confidential so i could not add this .

Kind regards,