| 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
male | 3.32 | 3.39 | 3.45 | 3.55 | 3.58 | 3.60 | 3.53 | 3.59 | 3.58 | 3.58 | 3.61 | 3.60 | 3.63 |
female | 3.35 | 3.39 | 3.46 | 3.54 | 3.60 | 3.57 | 3.55 | 3.60 | 3.58 | 3.56 | 3.60 | 3.61 | 3.62 |