| 年度 | 实际值 |
|---|---|
| 1995 | 37.1 |
| 1996 | 32.8 |
| 1997 | 37.42 |
| 1998 | 30.1 |
| 1999 | 31.3 |
| 2000 | 38.9 |
| 2001 | 39.02 |
| 2002 | 39.86 |
| 2003 | 39.54 |
| 2004 | 39.2 |
| 2005 | 34.26 |
| 2006 | 37.87 |
| 2007 | 38.87 |
| 2008 | 39.98 |
| 2009 | |
| 2010 | 41.82 |
| 2011 | 44.45 |
| 2012 | 45.68 |
| 2013 | 46.33 |
| 2014 | 44.69 |
| 2015 | 38.21 |
| 2016 | 27.17 |
| 2017 | |
| 2018 | 27.58 |