| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 17.6 | 38 |
| 2015 | 18.21 | 43 |
| 2014 | 18.79 | 44 |
| 2013 | 18.98 | 47 |
| 2012 | 19.24 | 45 |
| 2011 | 19.48 | 43 |
| 2010 | 19.81 | 43 |
| 2009 | 20.62 | 40 |
| 2008 | 21.85 | 42 |
| 2007 | 25.86 | 27 |
| 2006 | 27.9 | 26 |
| 2005 | 27.97 | 29 |
| 2004 | 30.77 | 24 |
| 2003 | 33.12 | 24 |
| 2002 | 34.25 | 22 |
| 2001 | 34.01 | 21 |
| 2000 | 34.36 | 21 |
| 1999 | 33.52 | 26 |
| 1998 | 31.31 | 30 |
| 1997 | 32.18 | 31 |
| 1996 | 26.14 | 41 |
| 1995 | 32.29 | 32 |
| 1994 | 37.43 | 22 |
| 1993 | 30.45 | 35 |
| 1992 | 34.83 | 25 |
| 1991 | 36.98 | 22 |
| 1990 | 32.76 | 26 |
| 1989 | 31.14 | 29 |
| 1988 | 29.26 | 34 |
| 1987 | 27.61 | 35 |