| 年度 | 实际值 |
|---|---|
| 1992 | 15.1 |
| 1993 | 14.3 |
| 1994 | |
| 1995 | 13.72 |
| 1996 | 13.61 |
| 1997 | 13.12 |
| 1998 | 5.39 |
| 1999 | 9.71 |
| 2000 | 18.15 |
| 2001 | 8.37 |
| 2002 | 8.85 |
| 2003 | 10.52 |
| 2004 | 12.28 |
| 2005 | 12.79 |
| 2006 | 15.24 |
| 2007 | 12.13 |
| 2008 | 9.5 |
| 2009 | |
| 2010 | 17.4 |
| 2011 | 11.8 |
| 2012 | 9.6 |
| 2013 | 13.6 |
| 2014 | 15.1 |
| 2015 | 13.83 |
| 2016 | 11.68 |
| 2017 | 14.68 |
| 2018 | 13.69 |