| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 20.3 | 130 |
| 2015 | 20.8 | 127 |
| 2014 | 20.7 | 130 |
| 2013 | 20.5 | 133 |
| 2012 | 20.4 | 136 |
| 2011 | 20.4 | 138 |
| 2010 | 20.3 | 139 |
| 2009 | 21.1 | 132 |
| 2008 | 21.9 | 132 |
| 2007 | 22.9 | 132 |
| 2006 | 24.2 | 130 |
| 2005 | 25.7 | 123 |
| 2004 | 26.4 | 122 |
| 2003 | 27.2 | 122 |
| 2002 | 28 | 120 |
| 2001 | 29.1 | 118 |
| 2000 | 30.1 | 116 |
| 1999 | 29.9 | 118 |
| 1998 | 29.8 | 120 |
| 1997 | 29.9 | 121 |
| 1996 | 30.1 | 122 |
| 1995 | 30.2 | 124 |
| 1994 | 30.8 | 122 |
| 1993 | 31.4 | 122 |
| 1992 | 32 | 121 |
| 1991 | 32.4 | 121 |
| 1990 | 32.7 | 121 |
| 1989 | 33 | 120 |
| 1988 | 33.2 | 121 |
| 1987 | 33.4 | 122 |
| 1986 | 33.6 | 123 |