| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 23.4 | 114 |
| 2015 | 23.7 | 112 |
| 2014 | 24.1 | 110 |
| 2013 | 24.5 | 110 |
| 2012 | 24.9 | 109 |
| 2011 | 25.4 | 109 |
| 2010 | 26 | 108 |
| 2009 | 26.3 | 110 |
| 2008 | 26.7 | 110 |
| 2007 | 27.1 | 110 |
| 2006 | 27.5 | 110 |
| 2005 | 27.8 | 111 |
| 2004 | 28.4 | 112 |
| 2003 | 28.9 | 111 |
| 2002 | 29.5 | 112 |
| 2001 | 30.1 | 114 |
| 2000 | 30.6 | 112 |
| 1999 | 31.3 | 111 |
| 1998 | 31.8 | 111 |
| 1997 | 32.4 | 112 |
| 1996 | 32.8 | 113 |
| 1995 | 33.2 | 113 |
| 1994 | 33.6 | 114 |
| 1993 | 33.9 | 114 |
| 1992 | 34.1 | 112 |
| 1991 | 34.4 | 113 |
| 1990 | 34.6 | 115 |
| 1989 | 35.1 | 113 |
| 1988 | 35.7 | 110 |
| 1987 | 36.5 | 110 |
| 1986 | 37.3 | 108 |