| 年度 | 实际值 |
|---|---|
| 1993 | 15.5 |
| 1994 | |
| 1995 | 17.6 |
| 1996 | 19.4 |
| 1997 | 21 |
| 1998 | 22.9 |
| 1999 | 23.5 |
| 2000 | 25 |
| 2001 | 1.74 |
| 2002 | |
| 2003 | 31.04 |
| 2004 | 35.02 |
| 2005 | 36 |
| 2006 | 5.55 |
| 2007 | 34.93 |
| 2008 | |
| 2009 | |
| 2010 | 30.31 |
| 2011 | 34.51 |
| 2012 | 34.89 |
| 2013 | 35.46 |
| 2014 | 41.82 |
| 2015 | 32.65 |
| 2016 | 32.81 |
| 2017 | 36.72 |
| 2018 | 38.03 |