| 年度 | 实际值 |
|---|---|
| 1992 | 4.4 |
| 1993 | .9 |
| 1994 | |
| 1995 | 2.11 |
| 1996 | 2.16 |
| 1997 | |
| 1998 | 5.43 |
| 1999 | 4.42 |
| 2000 | .85 |
| 2001 | 5.59 |
| 2002 | 5.13 |
| 2003 | 3.87 |
| 2004 | 5.11 |
| 2005 | 4.67 |
| 2006 | 4.41 |
| 2007 | 6.88 |
| 2008 | 4.53 |
| 2009 | |
| 2010 | 6.65 |
| 2011 | 9.1 |
| 2012 | 5.7 |
| 2013 | 6.9 |
| 2014 | 25.1 |
| 2015 | 17.91 |
| 2016 | 17.39 |
| 2017 | 13.42 |
| 2018 | 10.45 |