| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 15.2 | 168 |
| 2015 | 15.1 | 169 |
| 2014 | 14.9 | 171 |
| 2013 | 14.7 | 177 |
| 2012 | 14.4 | 183 |
| 2011 | 14.2 | 186 |
| 2010 | 14.1 | 185 |
| 2009 | 14 | 186 |
| 2008 | 14.1 | 188 |
| 2007 | 14.2 | 187 |
| 2006 | 14.5 | 186 |
| 2005 | 14.7 | 186 |
| 2004 | 15.2 | 184 |
| 2003 | 15.8 | 183 |
| 2002 | 16.5 | 181 |
| 2001 | 17.1 | 178 |
| 2000 | 17.9 | 176 |
| 1999 | 18.5 | 173 |
| 1998 | 19.1 | 170 |
| 1997 | 19.6 | 169 |
| 1996 | 20.2 | 167 |
| 1995 | 20.7 | 167 |
| 1994 | 21 | 167 |
| 1993 | 21.3 | 168 |
| 1992 | 21.4 | 168 |
| 1991 | 21.5 | 167 |
| 1990 | 21.5 | 169 |
| 1989 | 21.5 | 167 |
| 1988 | 21.5 | 171 |
| 1987 | 21.5 | 172 |
| 1986 | 21.4 | 173 |