| 年度 | 实际值 |
|---|---|
| 1992 | 13.2 |
| 1993 | 15 |
| 1994 | |
| 1995 | 18.24 |
| 1996 | 19.82 |
| 1997 | 17.05 |
| 1998 | 2.89 |
| 1999 | 16.17 |
| 2000 | 5.43 |
| 2001 | 7.27 |
| 2002 | 9.2 |
| 2003 | 7.59 |
| 2004 | 7.43 |
| 2005 | 8.41 |
| 2006 | 9.47 |
| 2007 | 4.93 |
| 2008 | 4.56 |
| 2009 | |
| 2010 | 5.54 |
| 2011 | 4.8 |
| 2012 | 3.6 |
| 2013 | 7.2 |
| 2014 | 4.9 |
| 2015 | 3.43 |
| 2016 | 6.07 |
| 2017 | 6.14 |
| 2018 | 4.67 |