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| Date of Survey | Instant/Follow-up survey | Successful Sample | Response Rate | Standard Error |
| 19-21/3/2007 | Follow-up survey | 1007 | 63.6% | 1.6% |
| 28/2/2007 | Instant survey | 1018 | 65.2% | 1.6% |
| 13-17/2/2006 | Follow-up survey | 1010 | 59.4% | 1.6% |
| 22/2/2006 | Instant survey | 1026 | 68.3% | 1.6% |
| 11-14/4/2005 | Follow-up survey | 1009 | 62.8% | 1.6% |
| 16/3/2005 | Instant survey | 1041 | 65.2% | 1.5% |
| 22-24/3/2004 | Follow-up survey | 1015 | 67.8% | 1.6% |
| 10/3/2004 | Instant survey | 1023 | 64.7% | 1.6% |
| 12-13/3/2003 | Follow-up survey | 1040 | 72.3% | 1.6% |
| 5/3/2003 | Instant survey | 1047 | 71.4% | 1.5% |
| 18-20/3/2002 | Follow-up survey | 1216 | 60.1% | 1.4% |
| 6/3/2002 | Instant survey | 1041 | 59.9% | 1.5% |
| 30-31/3/2001 | Follow-up survey | 511 | 73.3% | 2.2% |
| 7-8/3/2001 | Instant survey | 502 | 67.1% | 2.2% |
| 20/3/2000 | Follow-up survey | 660 | 56.7% | 2.0% |
| 8/3/2000 | Instant survey | 856 | 56.4% | 1.7% |
| 18/3/1999 | Follow-up survey | 530 | 55.4% | 2.2% |
| 3/3/1999 | Instant survey | 1190 | 62.1% | 1.8% |
| 24/2/1998 | Follow-up survey | 538 | 56.7% | 2.2% |
| 18/2/1998 | Instant survey | 804 | 54.7% | 1.8% |







