| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 16.9 | 154 |
| 2015 | 16.9 | 153 |
| 2014 | 17 | 152 |
| 2013 | 17.2 | 152 |
| 2012 | 17.4 | 152 |
| 2011 | 17.6 | 152 |
| 2010 | 17.8 | 153 |
| 2009 | 18.3 | 150 |
| 2008 | 18.7 | 149 |
| 2007 | 19.1 | 149 |
| 2006 | 19.6 | 147 |
| 2005 | 20 | 148 |
| 2004 | 20.5 | 147 |
| 2003 | 21 | 147 |
| 2002 | 21.5 | 146 |
| 2001 | 22 | 148 |
| 2000 | 22.4 | 149 |
| 1999 | 22.9 | 148 |
| 1998 | 23.4 | 148 |
| 1997 | 23.9 | 146 |
| 1996 | 24.2 | 146 |
| 1995 | 24.4 | 147 |
| 1994 | 24.7 | 146 |
| 1993 | 25 | 146 |
| 1992 | 25.2 | 146 |
| 1991 | 25.4 | 146 |
| 1990 | 25.5 | 146 |
| 1989 | 25.3 | 147 |
| 1988 | 25.2 | 149 |
| 1987 | 25.1 | 151 |
| 1986 | 25.1 | 152 |