| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.01 | 55 |
| 2015 | 4.28 | 41 |
| 2014 | 4.8 | 48 |
| 2013 | 7.1 | 93 |
| 2012 | 7.6 | 101 |
| 2011 | 7.33 | 95 |
| 2010 | 7.29 | 87 |
| 2009 | 7.24 | 87 |
| 2008 | 7.19 | 104 |
| 2007 | 7.15 | 99 |
| 2006 | 7.1 | 93 |
| 2005 | 7.06 | 81 |
| 2004 | 7.01 | 80 |
| 2003 | 6.93 | 78 |
| 2002 | 6.85 | 76 |
| 2001 | 6.78 | 75 |
| 2000 | 6.7 | 76 |
| 1999 | 5.93 | 59 |
| 1998 | 5.24 | 51 |
| 1997 | 4.63 | 45 |
| 1996 | 6.87 | 77 |
| 1995 | 6.25 | 65 |
| 1994 | 6.21 | 68 |
| 1993 | 6.2 | 73 |
| 1992 | 6.19 | 71 |
| 1991 | 5.94 | 73 |