| 年度 | 实际值 |
|---|---|
| 1992 | 5.1 |
| 1993 | 3.9 |
| 1994 | |
| 1995 | 4.74 |
| 1996 | 5.36 |
| 1997 | 6.16 |
| 1998 | 6.11 |
| 1999 | 5.51 |
| 2000 | 5.1 |
| 2001 | 6.24 |
| 2002 | 4.35 |
| 2003 | 4.43 |
| 2004 | 5.7 |
| 2005 | 4.62 |
| 2006 | 4.21 |
| 2007 | 2.02 |
| 2008 | 3.24 |
| 2009 | |
| 2010 | 3.46 |
| 2011 | 3.2 |
| 2012 | 2.1 |
| 2013 | 8.3 |
| 2014 | 14.9 |
| 2015 | 8.15 |
| 2016 | 11.92 |
| 2017 | 12.25 |
| 2018 | 10.07 |