Lying or Telling the Truth

We are taking one statement from each of eight people. The last two are Bill and Susan, or maybe Susan and Bill. Anyway, one of those two is Susan, the other is Bill. See if you can deduce which is Bill and which is Susan:

1. Exactly seven of us are lying.
2. Exactly six of us are lying.
3. Exactly five of us are lying.
4. Yes, exactly five of us are lying.
5. Exactly four of us are lying.
6. Exactly three of us are lying.
7. My name is Susan.
8. My name is Bill.