| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 15.2 | 169 |
| 2015 | 15.5 | 166 |
| 2014 | 15.8 | 164 |
| 2013 | 16.2 | 161 |
| 2012 | 16.6 | 160 |
| 2011 | 16.9 | 159 |
| 2010 | 17.3 | 158 |
| 2009 | 17.8 | 155 |
| 2008 | 18.2 | 154 |
| 2007 | 18.5 | 152 |
| 2006 | 18.8 | 153 |
| 2005 | 19.1 | 154 |
| 2004 | 19.5 | 154 |
| 2003 | 19.9 | 155 |
| 2002 | 20.4 | 156 |
| 2001 | 20.9 | 155 |
| 2000 | 21.5 | 153 |
| 1999 | 21.8 | 155 |
| 1998 | 22.2 | 154 |
| 1997 | 22.4 | 153 |
| 1996 | 22.5 | 154 |
| 1995 | 22.2 | 157 |
| 1994 | 22.2 | 159 |
| 1993 | 21.9 | 165 |
| 1992 | 21.6 | 167 |
| 1991 | 21.4 | 168 |
| 1990 | 21.5 | 168 |
| 1989 | 21.8 | 165 |
| 1988 | 22.4 | 164 |
| 1987 | 23.1 | 159 |
| 1986 | 23.8 | 159 |