| 年度 | 实际值 |
|---|---|
| 1995 | 36.9 |
| 1996 | 37.1 |
| 1997 | 36.25 |
| 1998 | 41.8 |
| 1999 | 40.3 |
| 2000 | 40 |
| 2001 | 36.47 |
| 2002 | 36.82 |
| 2003 | 35.26 |
| 2004 | 36.12 |
| 2005 | 32.43 |
| 2006 | 29.39 |
| 2007 | 29.04 |
| 2008 | 29.93 |
| 2009 | |
| 2010 | 23.77 |
| 2011 | 20.77 |
| 2012 | 19.59 |
| 2013 | 18.18 |
| 2014 | 16.93 |
| 2015 | 16.48 |
| 2016 | 16.13 |
| 2017 | |
| 2018 | 14.73 |