| 年度 | 实际值 |
|---|---|
| 1992 | 11.2 |
| 1993 | 11.2 |
| 1994 | |
| 1995 | 11.46 |
| 1996 | 10.49 |
| 1997 | 10.97 |
| 1998 | 4.93 |
| 1999 | 8.28 |
| 2000 | 8.13 |
| 2001 | 7.92 |
| 2002 | 5.79 |
| 2003 | 4.91 |
| 2004 | 5.24 |
| 2005 | 5.54 |
| 2006 | 7.86 |
| 2007 | 6.95 |
| 2008 | 6.36 |
| 2009 | |
| 2010 | 6.73 |
| 2011 | 7.5 |
| 2012 | 8 |
| 2013 | 7.9 |
| 2014 | 12.2 |
| 2015 | 13.56 |
| 2016 | 19.36 |
| 2017 | 13.78 |
| 2018 | 17.36 |