From what I have read, it appears that intelligent and informed people also happen to be the ones that vote (likely for social or ethical reasons). I have not seen evidence that mandatory (or strongly encouraged) voting leads to a more informed public; do you have any evidence of this?
No I don't, I was just wondering if it was discussed in the book you linked. But again, you're talking about a correlation in this comment, and I'm wondering which way the causation goes. I don't know if there are any studies on this.