How Many Characters Do You Kill Off in a Thriller Novel?

I've had this question posed to me recently and I had to stop and really think about it. How many characters are too many and how many are not enough to kill off in a thriller novel?

My first answer was… I'm not really sure. I don't think there is a special number of appropriate deaths for thriller novels.

I've just finished my second novel Dead Game and it's currently at the publishers where they will conduct their novel magic. It's extremely exciting to be working with a graphic artist and co...