| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.59 | 79 |
| 2015 | 8.77 | 78 |
| 2014 | 1.14 | 144 |
| 2013 | 8.94 | 86 |
| 2012 | 8.43 | 91 |
| 2011 | 12.18 | 73 |
| 2010 | 6.3 | 125 |
| 2009 | 4.17 | 123 |
| 2008 | 8.86 | 116 |
| 2007 | 31.29 | 40 |
| 2006 | 26.93 | 42 |
| 2005 | 21.49 | 49 |
| 2004 | 24.01 | 34 |
| 2003 | 20.2 | 43 |
| 2002 | 12.34 | 82 |
| 2001 | 25.96 | 47 |
| 2000 | 30.8 | 33 |
| 1999 | 13.37 | 82 |
| 1998 | 11.76 | 75 |
| 1997 | 351.45 | 1 |
| 1996 | 123.89 | 3 |
| 1995 | 40.46 | 24 |
| 1994 | 77.48 | 15 |
| 1993 | 53.88 | 18 |
| 1992 | 51.67 | 19 |