| 年度 | 实际值 |
|---|---|
| 1995 | 32.3 |
| 1996 | 32.2 |
| 1997 | 30.13 |
| 1998 | 30.9 |
| 1999 | 31.2 |
| 2000 | 35.2 |
| 2001 | 36.29 |
| 2002 | 42.04 |
| 2003 | 42.09 |
| 2004 | 43.48 |
| 2005 | 38.57 |
| 2006 | 39.84 |
| 2007 | 40.04 |
| 2008 | 38.1 |
| 2009 | |
| 2010 | 38.03 |
| 2011 | 39.44 |
| 2012 | 38.86 |
| 2013 | 38.32 |
| 2014 | 36.47 |
| 2015 | 33.2 |
| 2016 | 32.38 |
| 2017 | |
| 2018 | 32.12 |