| 年度 | 实际值 |
|---|---|
| 1995 | 26.1 |
| 1996 | 24.3 |
| 1997 | 22.54 |
| 1998 | 23.7 |
| 1999 | 30.7 |
| 2000 | 32.2 |
| 2001 | 32.36 |
| 2002 | 32.59 |
| 2003 | 32.92 |
| 2004 | 28.64 |
| 2005 | 28.02 |
| 2006 | 26.93 |
| 2007 | 26.26 |
| 2008 | 25.04 |
| 2009 | |
| 2010 | 23.22 |
| 2011 | 23.2 |
| 2012 | 24.65 |
| 2013 | 24.79 |
| 2014 | 30.78 |
| 2015 | 33.13 |
| 2016 | 34.33 |
| 2017 | |
| 2018 | 37.73 |