| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 19.6 | 69 |
| 2014 | 20.48 | 69 |
| 2013 | 20.61 | 77 |
| 2012 | 21.1 | 76 |
| 2011 | 22.12 | 71 |
| 2010 | 26.13 | 55 |
| 2009 | 19.06 | 84 |
| 2008 | 17.91 | 95 |
| 2007 | 15.93 | 104 |
| 2006 | 16.55 | 99 |
| 2005 | 16 | 98 |
| 2004 | 13.77 | 106 |
| 2003 | 14.76 | 95 |
| 2002 | 11.99 | 113 |
| 2001 | 11.11 | 118 |
| 2000 | 11.48 | 114 |
| 1999 | 10.17 | 117 |
| 1998 | 10.67 | 111 |
| 1997 | 15.13 | 76 |
| 1996 | 13.49 | 82 |
| 1995 | 13.81 | 79 |
| 1994 | 3.26 | 133 |
| 1993 | 3.51 | 132 |
| 1992 | 3.27 | 127 |
| 1991 | 4.06 | 121 |