| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 19.9 | 133 |
| 2015 | 19.8 | 134 |
| 2014 | 19.7 | 136 |
| 2013 | 19.6 | 139 |
| 2012 | 19.5 | 141 |
| 2011 | 19.4 | 143 |
| 2010 | 19.5 | 143 |
| 2009 | 19.6 | 143 |
| 2008 | 20 | 144 |
| 2007 | 20.4 | 141 |
| 2006 | 20.9 | 139 |
| 2005 | 21.5 | 140 |
| 2004 | 22.2 | 137 |
| 2003 | 23 | 135 |
| 2002 | 23.9 | 134 |
| 2001 | 24.8 | 133 |
| 2000 | 25.8 | 133 |
| 1999 | 26.6 | 130 |
| 1998 | 27.4 | 131 |
| 1997 | 28.1 | 131 |
| 1996 | 28.7 | 130 |
| 1995 | 29.3 | 128 |
| 1994 | 29.5 | 128 |
| 1993 | 29.8 | 130 |
| 1992 | 29.9 | 130 |
| 1991 | 30 | 131 |
| 1990 | 30 | 131 |
| 1989 | 30.1 | 132 |
| 1988 | 30 | 133 |
| 1987 | 30 | 134 |
| 1986 | 29.9 | 136 |