| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 20.2 | 131 |
| 2015 | 20.4 | 131 |
| 2014 | 20.4 | 131 |
| 2013 | 20.5 | 131 |
| 2012 | 20.6 | 133 |
| 2011 | 20.7 | 134 |
| 2010 | 20.8 | 134 |
| 2009 | 21 | 134 |
| 2008 | 21.3 | 135 |
| 2007 | 21.7 | 134 |
| 2006 | 22 | 133 |
| 2005 | 22.4 | 133 |
| 2004 | 22.9 | 133 |
| 2003 | 23.4 | 133 |
| 2002 | 24 | 133 |
| 2001 | 24.8 | 132 |
| 2000 | 25.9 | 132 |
| 1999 | 26.5 | 132 |
| 1998 | 27.1 | 132 |
| 1997 | 27.7 | 132 |
| 1996 | 27.9 | 132 |
| 1995 | 27.6 | 132 |
| 1994 | 27.7 | 134 |
| 1993 | 27.6 | 136 |
| 1992 | 27.5 | 138 |
| 1991 | 27.9 | 137 |
| 1990 | 28.8 | 135 |
| 1989 | 30 | 133 |
| 1988 | 31.4 | 128 |
| 1987 | 32.7 | 124 |
| 1986 | 33.5 | 124 |