| 年度 | 实际值 |
|---|---|
| 1995 | 34.1 |
| 1996 | 34.5 |
| 1997 | 28.77 |
| 1998 | 32.5 |
| 1999 | 32.4 |
| 2000 | 34.5 |
| 2001 | 42.15 |
| 2002 | 45.67 |
| 2003 | 45.39 |
| 2004 | 43.98 |
| 2005 | 40.21 |
| 2006 | 33.2 |
| 2007 | 31.43 |
| 2008 | 30.9 |
| 2009 | |
| 2010 | 29.53 |
| 2011 | 27.31 |
| 2012 | 26.93 |
| 2013 | 26.53 |
| 2014 | 29.54 |
| 2015 | 28.24 |
| 2016 | 29.6 |
| 2017 | 30.68 |
| 2018 | 32.72 |