| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 17.86 | 79 |
| 2014 | 20.51 | 67 |
| 2013 | 21.38 | 72 |
| 2012 | 22.23 | 71 |
| 2011 | 18.17 | 91 |
| 2010 | 17.63 | 90 |
| 2009 | 21.52 | 73 |
| 2008 | 20.43 | 78 |
| 2007 | 24.51 | 65 |
| 2006 | 26.49 | 54 |
| 2005 | 32.31 | 36 |
| 2004 | 38.79 | 27 |
| 2003 | 34.17 | 31 |
| 2002 | 32.29 | 32 |
| 2001 | 25.12 | 44 |
| 2000 | 21.13 | 54 |
| 1999 | 20.11 | 57 |
| 1998 | 20.06 | 59 |
| 1997 | 13.36 | 85 |
| 1996 | 12.52 | 86 |
| 1995 | 10.52 | 98 |
| 1994 | 14.76 | 76 |
| 1993 | 11.13 | 95 |
| 1992 | 7.36 | 112 |
| 1991 | 3.49 | 124 |
| 1990 | 7.11 | 107 |
| 1989 | 7.13 | 104 |
| 1988 | 9.82 | 78 |
| 1987 | 9.69 | 81 |
| 1986 | 9.53 | 83 |