| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 14.4 | 179 |
| 2015 | 14.4 | 182 |
| 2014 | 14.5 | 181 |
| 2013 | 14.6 | 179 |
| 2012 | 14.8 | 177 |
| 2011 | 15 | 175 |
| 2010 | 15.2 | 172 |
| 2009 | 15.6 | 168 |
| 2008 | 16 | 167 |
| 2007 | 16.5 | 167 |
| 2006 | 17.1 | 168 |
| 2005 | 17.7 | 164 |
| 2004 | 18.2 | 164 |
| 2003 | 18.7 | 163 |
| 2002 | 19.2 | 161 |
| 2001 | 19.6 | 161 |
| 2000 | 19.9 | 162 |
| 1999 | 20.3 | 162 |
| 1998 | 20.7 | 163 |
| 1997 | 21 | 163 |
| 1996 | 21.4 | 163 |
| 1995 | 21.8 | 161 |
| 1994 | 22.1 | 160 |
| 1993 | 22.5 | 159 |
| 1992 | 22.8 | 159 |
| 1991 | 23.2 | 159 |
| 1990 | 23.4 | 158 |
| 1989 | 23.6 | 156 |
| 1988 | 23.8 | 157 |
| 1987 | 24 | 157 |
| 1986 | 24.1 | 158 |