| 年度 | 实际值 |
|---|---|
| 1992 | 14.4 |
| 1993 | 13.9 |
| 1994 | |
| 1995 | 13.51 |
| 1996 | 13.67 |
| 1997 | 12.97 |
| 1998 | 5.18 |
| 1999 | 9.17 |
| 2000 | 13.82 |
| 2001 | 5.6 |
| 2002 | 9.41 |
| 2003 | 5.32 |
| 2004 | 4.76 |
| 2005 | 5.13 |
| 2006 | 5.73 |
| 2007 | 5.54 |
| 2008 | 5.86 |
| 2009 | |
| 2010 | 5.47 |
| 2011 | 6.1 |
| 2012 | 5.6 |
| 2013 | 12.7 |
| 2014 | 15.6 |
| 2015 | 7.66 |
| 2016 | 10.45 |
| 2017 | 11.24 |
| 2018 | 11.72 |