| 年度 | 实际值 |
|---|---|
| 1992 | 14.4 |
| 1993 | 14.3 |
| 1994 | |
| 1995 | 14.5 |
| 1996 | 15.49 |
| 1997 | 13.61 |
| 1998 | 3.99 |
| 1999 | 11.87 |
| 2000 | 9.89 |
| 2001 | 9.84 |
| 2002 | 11.62 |
| 2003 | 10.2 |
| 2004 | 8.99 |
| 2005 | 9.72 |
| 2006 | 11.87 |
| 2007 | 15.29 |
| 2008 | 12.66 |
| 2009 | |
| 2010 | 12.53 |
| 2011 | 21.3 |
| 2012 | 5.2 |
| 2013 | 16.2 |
| 2014 | 18.2 |
| 2015 | 18.11 |
| 2016 | 21.1 |
| 2017 | 29.33 |
| 2018 | 13.47 |