| 年度 | 实际值 |
|---|---|
| 1995 | 41.9 |
| 1996 | 39.1 |
| 1997 | 20.86 |
| 1998 | 38.4 |
| 1999 | 39.3 |
| 2000 | 41.4 |
| 2001 | 43.13 |
| 2002 | 42.33 |
| 2003 | 42.71 |
| 2004 | 39.82 |
| 2005 | |
| 2006 | 37.44 |
| 2007 | 32.43 |
| 2008 | 30.52 |
| 2009 | |
| 2010 | 33.46 |
| 2011 | 34.19 |
| 2012 | 33.47 |
| 2013 | 30.54 |
| 2014 | 29.03 |
| 2015 | 30.35 |
| 2016 | 30.61 |
| 2017 | 31.15 |
| 2018 | 35.83 |