Dropdown of dates, is it acceptable to display in non-chronological order?

We have a time-series graph. The user can use a drop-down to select their years and these years are displayed on the chart. Currently, the dropdown is just a list of years for the past 30 years.

My superior is discussing ordering the dropdown, not by chronological order of years, but based on a value, such as the busiest year. My concern with this is that there will not be an expected order to the dropdown. Years will be all over the place, 2017 might be at the bottom whilst 2019 might be at the top.

I think it's very confusing to anyone trying to find a year. So I suggested we find a different way. They're suggesting we use a checkbox to modify the dropdown. Eg, default to chronological and change the drop-down to busiest to least-busy year if the checkbox is selected. I still have issues with this as I'm yet to see a website use boolean modifiers against a drop-down, I think we'll struggle to make it clear the link between the dropbox and the checkbox.

Any suggestions?