I'm trying to create a single legend for multiple maps. Each map is for a different year, and has the same set of polygons. The polygons on each map display a different range of values.
For example data for 2010 is from min 3 to max 10 and data from 2016 is from min 5 to max 12. I want a single legend that shows the entire range of values, from min 3 to max 12.
How can I create a single legend that covers the range of values on both maps?