| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 22.1 | 119 |
| 2015 | 22.5 | 119 |
| 2014 | 23 | 118 |
| 2013 | 23.4 | 115 |
| 2012 | 23.9 | 113 |
| 2011 | 24.4 | 115 |
| 2010 | 24.9 | 114 |
| 2009 | 25.4 | 114 |
| 2008 | 25.9 | 113 |
| 2007 | 26.4 | 113 |
| 2006 | 26.9 | 113 |
| 2005 | 27.4 | 115 |
| 2004 | 28 | 115 |
| 2003 | 28.5 | 116 |
| 2002 | 29.1 | 115 |
| 2001 | 29.6 | 115 |
| 2000 | 30.1 | 117 |
| 1999 | 30.7 | 116 |
| 1998 | 31.3 | 115 |
| 1997 | 31.9 | 115 |
| 1996 | 32.5 | 115 |
| 1995 | 33 | 115 |
| 1994 | 33.6 | 115 |
| 1993 | 34.1 | 111 |
| 1992 | 34.5 | 111 |
| 1991 | 35 | 110 |
| 1990 | 35.5 | 111 |
| 1989 | 35.8 | 108 |
| 1988 | 36.2 | 109 |
| 1987 | 36.5 | 109 |
| 1986 | 36.8 | 110 |