| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 21.7 | 123 |
| 2015 | 21.7 | 123 |
| 2014 | 21.6 | 124 |
| 2013 | 21.4 | 127 |
| 2012 | 21.2 | 129 |
| 2011 | 21 | 132 |
| 2010 | 20.7 | 136 |
| 2009 | 20.6 | 139 |
| 2008 | 20.4 | 140 |
| 2007 | 20.3 | 144 |
| 2006 | 20.2 | 144 |
| 2005 | 20.2 | 147 |
| 2004 | 20.2 | 149 |
| 2003 | 20.4 | 153 |
| 2002 | 20.6 | 154 |
| 2001 | 21 | 154 |
| 2000 | 21.4 | 155 |
| 1999 | 21.8 | 154 |
| 1998 | 22.3 | 150 |
| 1997 | 22.9 | 150 |
| 1996 | 23.6 | 148 |
| 1995 | 24.2 | 148 |
| 1994 | 24.9 | 145 |
| 1993 | 25.5 | 144 |
| 1992 | 26.1 | 142 |
| 1991 | 26.8 | 140 |
| 1990 | 27.5 | 139 |
| 1989 | 28.1 | 137 |
| 1988 | 28.7 | 137 |
| 1987 | 29.2 | 137 |
| 1986 | 29.7 | 137 |