| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 21.2 | 124 |
| 2015 | 21.4 | 124 |
| 2014 | 21.6 | 123 |
| 2013 | 21.8 | 123 |
| 2012 | 22 | 124 |
| 2011 | 22.3 | 127 |
| 2010 | 22.5 | 128 |
| 2009 | 22.8 | 130 |
| 2008 | 23 | 131 |
| 2007 | 23.3 | 131 |
| 2006 | 23.5 | 132 |
| 2005 | 23.8 | 132 |
| 2004 | 24 | 132 |
| 2003 | 24.1 | 132 |
| 2002 | 24.3 | 132 |
| 2001 | 24.4 | 136 |
| 2000 | 24.6 | 139 |
| 1999 | 24.7 | 139 |
| 1998 | 24.7 | 141 |
| 1997 | 24.8 | 141 |
| 1996 | 24.9 | 143 |
| 1995 | 25 | 144 |
| 1994 | 25.2 | 144 |
| 1993 | 25.4 | 145 |
| 1992 | 25.7 | 145 |
| 1991 | 25.9 | 144 |
| 1990 | 26 | 144 |
| 1989 | 26.2 | 143 |
| 1988 | 26.4 | 144 |
| 1987 | 26.5 | 144 |
| 1986 | 26.6 | 144 |