Define width for yAxis labels

[nat-jones]

I have the following pair of charts displayed on the same page.

If you look closely, you can see that the top chart Y-axis labels are ever-so-slightly narrower that the bottom chart. This leads to the graphs not lining up with each other vertically, despite having the same domain and chart width to work with.

I would like to find a way to strictly define the width of the yAxis labels so I can line up the charts exactly underneath each other. does anyone know how to do this, or have alternative suggestions?