Entering Data for Graphs - Illustrator CC

I'm entering data for graphs I'm making in Illustrator, and notice that value labels (for the X axis in this case) need to be put in quotation marks in order for them to appear on the X axis. The value labels are years - 1991, 1992, 1993, etc.

Is there a workaround for this / do I have to use quotation marks every single time, for each value?

Thanks for any thoughts.