| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 14.2 | 182 |
| 2015 | 14.5 | 180 |
| 2014 | 14.6 | 177 |
| 2013 | 14.9 | 171 |
| 2012 | 15.3 | 168 |
| 2011 | 15.6 | 167 |
| 2010 | 15.7 | 167 |
| 2009 | 16.1 | 166 |
| 2008 | 16.4 | 166 |
| 2007 | 16.7 | 166 |
| 2006 | 17.1 | 166 |
| 2005 | 17.7 | 165 |
| 2004 | 18.3 | 163 |
| 2003 | 18.9 | 160 |
| 2002 | 19.7 | 160 |
| 2001 | 20.3 | 157 |
| 2000 | 20.7 | 157 |
| 1999 | 21.1 | 156 |
| 1998 | 21.3 | 157 |
| 1997 | 21.5 | 159 |
| 1996 | 21.7 | 159 |
| 1995 | 22 | 160 |
| 1994 | 22.3 | 158 |
| 1993 | 22.7 | 157 |
| 1992 | 23.2 | 156 |
| 1991 | 23.7 | 154 |
| 1990 | 24.2 | 154 |
| 1989 | 24.6 | 153 |
| 1988 | 25 | 151 |
| 1987 | 25.4 | 150 |
| 1986 | 25.8 | 149 |