| 时间 | 值 | 世界排名 |
|---|---|---|
| 2013 | 4 | 82 |
| 2012 | 3.3 | 106 |
| 2011 | 3.3 | 100 |
| 2010 | 3.4 | 113 |
| 2009 | 3.6 | 111 |
| 2008 | 2.5 | 100 |
| 2007 | 2.7 | 108 |
| 2006 | 2.7 | 108 |
| 2005 | 2.6 | 101 |
| 2004 | 3.7 | 66 |
| 2003 | 2.7 | 92 |
| 2002 | 3.3 | 77 |
| 2001 | 2.4 | 89 |
| 2000 | 2 | 103 |
| 1999 | 2.1 | 105 |
| 1998 | 2 | 96 |
| 1997 | 2.2 | 94 |
| 1996 | 2 | 95 |
| 1995 | 2.4 | 79 |
| 1994 | 2.1 | 90 |
| 1993 | 1.9 | 88 |
| 1992 | 2.1 | 81 |
| 1991 | 1.3 | 105 |
| 1990 | 1.4 | 93 |
| 1989 | 1.3 | 96 |
| 1988 | 1.6 | 87 |
| 1987 | 2.2 | 78 |
| 1986 | 2.2 | 77 |