| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 18 | 77 |
| 2014 | 21.01 | 64 |
| 2013 | 19.52 | 84 |
| 2012 | 19.87 | 80 |
| 2011 | 23.44 | 67 |
| 2010 | 23.78 | 62 |
| 2009 | 26.22 | 53 |
| 2008 | 26.69 | 55 |
| 2007 | 21.43 | 76 |
| 2006 | 21.53 | 71 |
| 2005 | 24.68 | 57 |
| 2004 | 26.1 | 51 |
| 2003 | 24.82 | 49 |
| 2002 | 28.24 | 41 |
| 2001 | 41.64 | 23 |
| 2000 | 32.5 | 29 |
| 1999 | 44.65 | 18 |
| 1998 | 42.78 | 21 |
| 1997 | 35.88 | 26 |
| 1996 | 35.75 | 26 |
| 1995 | 42.95 | 20 |
| 1994 | 42.2 | 21 |
| 1993 | 31.6 | 27 |
| 1992 | 38.44 | 21 |
| 1991 | 16.59 | 56 |
| 1990 | 19.11 | 46 |
| 1989 | 13.21 | 67 |
| 1988 | 18.88 | 42 |
| 1987 | 7.72 | 93 |
| 1986 | 10.52 | 71 |