| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 13.9 | 185 |
| 2015 | 13.8 | 188 |
| 2014 | 13.7 | 188 |
| 2013 | 13.6 | 188 |
| 2012 | 13.6 | 187 |
| 2011 | 13.5 | 188 |
| 2010 | 13.4 | 189 |
| 2009 | 13.9 | 188 |
| 2008 | 14.5 | 183 |
| 2007 | 15.4 | 177 |
| 2006 | 16.7 | 169 |
| 2005 | 18.4 | 161 |
| 2004 | 19.3 | 156 |
| 2003 | 20.5 | 150 |
| 2002 | 22 | 144 |
| 2001 | 23.9 | 138 |
| 2000 | 26 | 130 |
| 1999 | 26.1 | 134 |
| 1998 | 26.2 | 136 |
| 1997 | 26.5 | 136 |
| 1996 | 26.9 | 136 |
| 1995 | 27.3 | 136 |
| 1994 | 28 | 132 |
| 1993 | 28.7 | 132 |
| 1992 | 29.4 | 132 |
| 1991 | 30.2 | 129 |
| 1990 | 30.9 | 128 |
| 1989 | 31.4 | 126 |
| 1988 | 31.8 | 126 |
| 1987 | 32 | 127 |
| 1986 | 32.1 | 127 |