I like the fact that there are popups that appear when you hover over the different tax rate options.  However, the information in the popups does not appear to be accurate.  I have included a series of screen snapshots of the different popups and what actually happens when you select each tax rate.

This popup appears when you hover over the "Normal" tax rate button when it is already selected.  The information in it is what I would expect.

The next popup appears when you hover over the "Medium" tax rate button when the "Normal" tax rate is in effect.

Given what it says, I would expect that when I click on the "Medium" button my civilization's approval should go to 87% (91% - 4%), but as the following screen snapshot shows, my civilization's approval goes to 82%, a reduction of 9% not 4%.

Now, with the "Medium" tax rate selected, when I hover over the "Low" tax rate button the following screen snapshot shows what the popup says.

Given what it says, I would expect that when I click on the "Low" button my civilization's approval should go to 93% (82% + 11%), but as the following screen snapshot shows, my civilization's approval goes to 96%, an increase of 14%, not 11%.

The "High" and "Max" buttons have the same issue, but I won't waste time and space documenting them here.

Bottom line, I think it is great that you have the popups to give players information about what effect each tax rate will have, but you need to make the information ACCURATE!