| S/N | Year | Mean | Departure from Mean | X |
| 1 | 2003 | 85 | 3.4375 | 81.5625 |
| 2 | 2004 | 84 | 2.4375 | 81.5625 |
| 3 | 2005 | 85 | 3.4375 | 81.5625 |
| 4 | 2006 | 85 | 3.4375 | 81.5625 |
| 5 | 2007 | 82 | 0.4375 | 81.5625 |
| 6 | 2008 | 83 | 1.4375 | 81.5625 |
| 7 | 2009 | 83 | 3.4375 | 81.5625 |
| 8 | 2010 | 85 | 3.4375 | 81.5625 |
| 9 | 2011 | 78.64 | −2.9225 | 81.5625 |
| 10 | 2012 | 76 | −5.5625 | 81.5625 |