| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 55.4 | 163 |
| 2015 | 54.9 | 165 |
| 2014 | 54.3 | 166 |
| 2013 | 53.8 | 172 |
| 2012 | 53.3 | 173 |
| 2011 | 52.7 | 178 |
| 2010 | 52.2 | 178 |
| 2009 | 51.8 | 179 |
| 2008 | 51.5 | 180 |
| 2007 | 51.1 | 180 |
| 2006 | 50.9 | 184 |
| 2005 | 50.7 | 184 |
| 2004 | 50.6 | 184 |
| 2003 | 50.5 | 183 |
| 2002 | 50.4 | 183 |
| 2001 | 50.4 | 182 |
| 2000 | 50.4 | 181 |
| 1999 | 50.3 | 181 |
| 1998 | 50.2 | 183 |
| 1997 | 50.2 | 183 |
| 1996 | 50.2 | 182 |
| 1995 | 50.3 | 180 |
| 1994 | 50.3 | 177 |
| 1993 | 50.3 | 178 |
| 1992 | 50.3 | 176 |
| 1991 | 50.4 | 174 |
| 1990 | 50.6 | 171 |
| 1989 | 50.6 | 168 |
| 1988 | 50.6 | 164 |
| 1987 | 50.6 | 163 |
| 1986 | 50.7 | 161 |