How big is the bonus?

[ChrisShaffer]

So, how much extra commerce do you actually get in the city center if you are Commercial? How many extra shields do you get if you're Industrious? I'm playing my first game as the Indians, and my cities just hit size 7-12 and it's amazing! My cities on rivers, in monarchy, are producing 5 trade in the city center. That's +3. Will it be even more when I hit size 13+ ? Do the same numbers hold for Industrious civs also?