| 年度 | 实际值 |
|---|---|
| 1992 | 4.6 |
| 1993 | 4 |
| 1994 | |
| 1995 | 1.11 |
| 1996 | 2.02 |
| 1997 | 3.21 |
| 1998 | 6.56 |
| 1999 | 2.97 |
| 2000 | 3.5 |
| 2001 | 3.04 |
| 2002 | 4.49 |
| 2003 | 4.73 |
| 2004 | 8.28 |
| 2005 | 9.36 |
| 2006 | 11.7 |
| 2007 | 14.74 |
| 2008 | 13.66 |
| 2009 | |
| 2010 | 16.18 |
| 2011 | 14.4 |
| 2012 | 8.6 |
| 2013 | 7.2 |
| 2014 | 6.2 |
| 2015 | 4.93 |
| 2016 | 4.98 |
| 2017 | 4.81 |
| 2018 | 8.07 |