| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.61 | 67 |
| 2015 | 5.25 | 58 |
| 2014 | 5.89 | 71 |
| 2013 | 6.21 | 74 |
| 2012 | 6.86 | 87 |
| 2011 | 7.14 | 90 |
| 2010 | 8.48 | 109 |
| 2009 | 9.53 | 127 |
| 2008 | 7.7 | 113 |
| 2007 | 9.38 | 136 |
| 2006 | 10.71 | 139 |
| 2005 | 11.34 | 140 |
| 2004 | 13.03 | 148 |
| 2003 | 13.51 | 146 |
| 2002 | 12.89 | 141 |
| 2001 | 11.81 | 136 |
| 2000 | 11.1 | 125 |
| 1999 | 11.18 | 119 |
| 1998 | 10.75 | 121 |
| 1997 | 9.75 | 112 |
| 1996 | 8.45 | 97 |
| 1995 | 8.78 | 106 |
| 1994 | 9.93 | 118 |
| 1993 | 12.74 | 136 |
| 1992 | 14.08 | 141 |
| 1991 | 13.39 | 143 |