| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 14.8 | 174 |
| 2015 | 14.9 | 173 |
| 2014 | 14.9 | 173 |
| 2013 | 15 | 170 |
| 2012 | 15.1 | 172 |
| 2011 | 15.2 | 171 |
| 2010 | 15.2 | 171 |
| 2009 | 15.4 | 172 |
| 2008 | 15.6 | 171 |
| 2007 | 15.9 | 171 |
| 2006 | 16.2 | 172 |
| 2005 | 16.6 | 173 |
| 2004 | 17.1 | 173 |
| 2003 | 17.6 | 171 |
| 2002 | 18.2 | 170 |
| 2001 | 18.8 | 166 |
| 2000 | 19.6 | 164 |
| 1999 | 20.3 | 163 |
| 1998 | 21 | 159 |
| 1997 | 21.8 | 157 |
| 1996 | 22.5 | 155 |
| 1995 | 23 | 151 |
| 1994 | 23.6 | 150 |
| 1993 | 24.1 | 150 |
| 1992 | 24.4 | 151 |
| 1991 | 24.7 | 151 |
| 1990 | 25.1 | 150 |
| 1989 | 25.3 | 148 |
| 1988 | 25.5 | 147 |
| 1987 | 25.7 | 149 |
| 1986 | 25.7 | 151 |