| 年度 | 实际值 |
|---|---|
| 1995 | 35.1 |
| 1996 | 38.5 |
| 1997 | 35.77 |
| 1998 | 36.7 |
| 1999 | 33.3 |
| 2000 | 28.1 |
| 2001 | 28.37 |
| 2002 | 28.39 |
| 2003 | 26.24 |
| 2004 | 27.29 |
| 2005 | 26.53 |
| 2006 | 23.1 |
| 2007 | 20.58 |
| 2008 | 19.08 |
| 2009 | |
| 2010 | 16.33 |
| 2011 | 15.64 |
| 2012 | 15.14 |
| 2013 | 15.7 |
| 2014 | 15.43 |
| 2015 | 14.88 |
| 2016 | 15.12 |
| 2017 | |
| 2018 | 19.74 |