| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 19.8 | 134 |
| 2015 | 20 | 133 |
| 2014 | 20.1 | 134 |
| 2013 | 20.2 | 135 |
| 2012 | 20.4 | 135 |
| 2011 | 20.5 | 137 |
| 2010 | 20.5 | 138 |
| 2009 | 20.7 | 138 |
| 2008 | 20.9 | 138 |
| 2007 | 21.1 | 137 |
| 2006 | 21.3 | 137 |
| 2005 | 21.5 | 138 |
| 2004 | 21.8 | 140 |
| 2003 | 22 | 142 |
| 2002 | 22.3 | 143 |
| 2001 | 22.5 | 145 |
| 2000 | 22.7 | 146 |
| 1999 | 22.9 | 149 |
| 1998 | 23 | 149 |
| 1997 | 23 | 149 |
| 1996 | 23 | 151 |
| 1995 | 23 | 153 |
| 1994 | 23.1 | 154 |
| 1993 | 23.1 | 155 |
| 1992 | 23.1 | 157 |
| 1991 | 23.2 | 158 |
| 1990 | 23.2 | 159 |
| 1989 | 23.4 | 158 |
| 1988 | 23.6 | 158 |
| 1987 | 24 | 158 |
| 1986 | 24.3 | 157 |