| 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
Primary | 3.43 | 3.43 | 3.52 | 3.58 | 3.63 | 3.43 | 3.60 | 3.68 | 3.65 | 3.59 | 3.67 | 3.71 | 3.73 |
Secondary | 3.33 | 3.38 | 3.39 | 3.54 | 3.56 | 3.58 | 3.52 | 3.57 | 3.57 | 3.55 | 3.61 | 3.72 | 3.71 |
Higher | 3.30 | 3.46 | 3.46 | 3.52 | 3.95 | 3.55 | 3.48 | 3.60 | 3.58 | 3.57 | 3.63 | 3.72 | 3.59 |