| 年度 | 实际值 |
|---|---|
| 1992 | 4.6 |
| 1993 | 4 |
| 1994 | |
| 1995 | 1.38 |
| 1996 | 2.23 |
| 1997 | 3.46 |
| 1998 | 5.93 |
| 1999 | 4 |
| 2000 | 6.43 |
| 2001 | 4.85 |
| 2002 | 5.86 |
| 2003 | 6.29 |
| 2004 | 8.3 |
| 2005 | 10.31 |
| 2006 | 11.97 |
| 2007 | 13.12 |
| 2008 | 12.31 |
| 2009 | |
| 2010 | 14.01 |
| 2011 | 11.9 |
| 2012 | 12.9 |
| 2013 | 11.8 |
| 2014 | 5.1 |
| 2015 | 5.21 |
| 2016 | 6.08 |
| 2017 | 6.63 |
| 2018 | 9.02 |