| 09/03/2008 | - | 32.1% | 64.2% |
| 08/27/2008 | 09/02/2008 | 32.3% | 64.6% |
| 08/20/2008 | 08/26/2008 | 32.9% | 65.8% |
| 08/13/2008 | 08/19/2008 | 34.4% | 68.8% |
| 08/06/2008 | 08/12/2008 | 35.9% | 71.8% |
| 07/30/2008 | 08/05/2008 | 36.9% | 73.8% |
| 07/23/2008 | 07/29/2008 | 38.0% | 76.0% |
| 07/16/2008 | 07/22/2008 | 38.5% | 77.0% |
| 07/09/2008 | 07/15/2008 | 38.1% | 76.2% |
| 06/25/2008 | 07/08/2008 | 37.3% | 74.6% |
| 06/11/2008 | 06/24/2008 | 37.8% | 75.6% |
| 06/04/2008 | 06/10/2008 | 37.9% | 75.8% |
| 05/28/2008 | 06/03/2008 | 38.1% | 76.2% |
| 05/21/2008 | 05/27/2008 | 35.8% | 71.6% |
| 05/14/2008 | 05/20/2008 | 34.2% | 68.4% |
| 05/07/2008 | 05/13/2008 | 32.3% | 64.6% |
| 04/30/2008 | 05/06/2008 | 32.6% | 65.2% |
| 04/23/2008 | 04/29/2008 | 32.3% | 64.6% |
| 04/16/2008 | 04/22/2008 | 31.4% | 62.8% |
| 04/09/2008 | 04/15/2008 | 30.4% | 60.8% |
| 04/02/2008 | 04/08/2008 | 30.5% | 61.0% |
| 03/26/2008 | 04/01/2008 | 30.7% | 61.4% |
| 03/19/2008 | 03/25/2008 | 30.6% | 61.2% |
| 03/12/2008 | 03/18/2008 | 29.0% | 58.0% |
| 03/05/2008 | 03/11/2008 | 27.4% | 54.8% |
| 02/27/2008 | 03/04/2008 | 26.4% | 52.8% |
| 02/20/2008 | 02/26/2008 | 24.8% | 49.6% |
| 02/06/2008 | 02/19/2008 | 23.7% | 47.4% |
| 01/30/2008 | 02/05/2008 | 23.4% | 46.8% |
| 01/23/2008 | 01/29/2008 | 23.6% | 47.2% |
| 01/16/2008 | 01/22/2008 | 24.1% | 48.2% |
| 01/09/2008 | 01/15/2008 | 24.6% | 49.2% |
| 01/02/2008 | 01/08/2008 | 24.3% | 48.6% |
| 12/19/2007 | 01/01/2008 | 23.9% | 47.8% |
| 12/12/2007 | 12/18/2007 | 24.1% | 48.2% |
| 12/05/2007 | 12/11/2007 | 25.0% | 50.0% |
| 11/28/2007 | 12/04/2007 | 25.3% | 50.6% |
| 11/21/2007 | 11/27/2007 | 25.0% | 50.0% |
| 11/14/2007 | 11/20/2007 | 25.1% | 50.2% |
| 11/07/2007 | 11/13/2007 | 23.9% | 47.8% |
| 10/31/2007 | 11/06/2007 | 22.4% | 44.8% |
| 10/24/2007 | 10/30/2007 | 21.8% | 43.6% |
| 10/10/2007 | 10/23/2007 | 21.2% | 42.4% |
| 10/03/2007 | 10/09/2007 | 21.3% | 42.6% |
| 09/26/2007 | 10/02/2007 | 21.2% | 42.4% |
| 09/19/2007 | 09/25/2007 | 20.5% | 41.0% |
| 09/12/2007 | 09/18/2007 | 20.1% | 40.2% |
| 09/08/2007 | 09/11/2007 | 19.8% | 39.6% |