| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 13.9 | 186 |
| 2015 | 13.8 | 187 |
| 2014 | 13.7 | 189 |
| 2013 | 13.5 | 189 |
| 2012 | 13.4 | 189 |
| 2011 | 13.3 | 192 |
| 2010 | 13.1 | 192 |
| 2009 | 13.7 | 189 |
| 2008 | 14.7 | 181 |
| 2007 | 16.3 | 168 |
| 2006 | 18.6 | 155 |
| 2005 | 21.7 | 137 |
| 2004 | 22.2 | 138 |
| 2003 | 22.8 | 137 |
| 2002 | 23.5 | 136 |
| 2001 | 24.5 | 135 |
| 2000 | 25.7 | 135 |
| 1999 | 25.9 | 136 |
| 1998 | 26.3 | 135 |
| 1997 | 26.6 | 135 |
| 1996 | 27 | 134 |
| 1995 | 27.3 | 135 |
| 1994 | 27.5 | 137 |
| 1993 | 27.6 | 137 |
| 1992 | 27.7 | 136 |
| 1991 | 27.9 | 136 |
| 1990 | 28.3 | 137 |
| 1989 | 28.6 | 136 |
| 1988 | 28.9 | 136 |
| 1987 | 29.1 | 138 |
| 1986 | 29.2 | 139 |