Do you have to display it on timescale?
If not then you can create 3 sheets and 2 parameters to handle that.
Create 2 parameters for start and end date and 1 calculated field keeping result of your calculation.
Create 2 sheets and on each display bar or point from your parameter.
Then create 1 new sheet and pull this new calculated field on label.
Pull sheets on dashboard so you have 1 sheet with start date bar, sheet with label and second sheet with end date.
ultimately you can change those parameter bars just to labels so you will have 3 labels (start year, growth and end date). You can tweak it further to show it as a growth in graphical way.