I suggest two columns. One numeric, (without the % character) on which you can do statistics, calculations, and other kinds of math, and a second column, text/string data type, where the values are based on an expression/formula of the value in the first column, formatting the value as a string (converted from the number in the original column) with a percent character concatenated onto the end. That column you can use for, say, labeling and such. You won’t actually be doing math on that column.

Then when a value changes in the first column, the formula/expression automagically changes that row’s value in the second column.

Exactly how to do this depends on which software you’re using, but conceptually I’d do this as two columns like that.

In excel this would be a formula. In ArcGIS this could be done with Arcade.