| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 13.7 | 188 |
| 2015 | 13.9 | 186 |
| 2014 | 14.2 | 184 |
| 2013 | 14.6 | 178 |
| 2012 | 15.1 | 171 |
| 2011 | 15.6 | 166 |
| 2010 | 16.1 | 165 |
| 2009 | 16.7 | 162 |
| 2008 | 17.2 | 160 |
| 2007 | 17.8 | 159 |
| 2006 | 18.3 | 158 |
| 2005 | 18.8 | 155 |
| 2004 | 19.2 | 157 |
| 2003 | 19.5 | 157 |
| 2002 | 19.8 | 159 |
| 2001 | 20.1 | 159 |
| 2000 | 20.6 | 158 |
| 1999 | 21 | 157 |
| 1998 | 21.6 | 156 |
| 1997 | 22.3 | 154 |
| 1996 | 22.8 | 152 |
| 1995 | 23 | 152 |
| 1994 | 23.5 | 152 |
| 1993 | 23.8 | 152 |
| 1992 | 24.1 | 152 |
| 1991 | 24.6 | 152 |
| 1990 | 25.4 | 148 |
| 1989 | 26.2 | 144 |
| 1988 | 27.2 | 142 |
| 1987 | 28.3 | 140 |
| 1986 | 29.3 | 138 |