| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 18.1 | 82 |
| 2013 | 18.71 | 91 |
| 2012 | 17.95 | 94 |
| 2011 | 17.1 | 98 |
| 2010 | 16.75 | 97 |
| 2009 | 16.92 | 95 |
| 2008 | 20.14 | 81 |
| 2007 | 21.61 | 74 |
| 2006 | 17.56 | 94 |
| 2005 | 18.06 | 88 |
| 2004 | 16.98 | 87 |
| 2003 | 16.89 | 82 |
| 2002 | 17.64 | 77 |
| 2001 | 16.65 | 78 |
| 2000 | 16.88 | 73 |
| 1999 | 16.43 | 72 |
| 1998 | 17.28 | 66 |
| 1997 | 16.27 | 69 |
| 1996 | 15.2 | 75 |
| 1995 | 22.36 | 42 |
| 1994 | 23.34 | 41 |
| 1993 | 17.52 | 61 |
| 1992 | 18.91 | 49 |
| 1991 | 19.07 | 43 |
| 1990 | 20.82 | 41 |
| 1989 | 18.57 | 45 |
| 1988 | 18.4 | 45 |
| 1987 | 17.21 | 48 |
| 1986 | 19.55 | 42 |