| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 15.3 | 166 |
| 2015 | 15.4 | 167 |
| 2014 | 15.5 | 167 |
| 2013 | 15.6 | 166 |
| 2012 | 15.7 | 164 |
| 2011 | 15.8 | 165 |
| 2010 | 15.8 | 166 |
| 2009 | 15.7 | 167 |
| 2008 | 15.7 | 170 |
| 2007 | 15.6 | 174 |
| 2006 | 15.7 | 177 |
| 2005 | 15.9 | 177 |
| 2004 | 16.3 | 176 |
| 2003 | 16.9 | 174 |
| 2002 | 17.6 | 173 |
| 2001 | 18.1 | 171 |
| 2000 | 18.5 | 169 |
| 1999 | 19 | 168 |
| 1998 | 19.4 | 168 |
| 1997 | 19.6 | 168 |
| 1996 | 20.1 | 168 |
| 1995 | 20.8 | 166 |
| 1994 | 21.4 | 166 |
| 1993 | 22.1 | 163 |
| 1992 | 22.9 | 158 |
| 1991 | 23.5 | 157 |
| 1990 | 23.7 | 157 |
| 1989 | 24.2 | 155 |
| 1988 | 24.4 | 155 |
| 1987 | 24.5 | 156 |
| 1986 | 24.7 | 155 |