| 年度 | 实际值 |
|---|---|
| 1995 | 30.6 |
| 1996 | 30.7 |
| 1997 | 28.54 |
| 1998 | 29.3 |
| 1999 | 31.9 |
| 2000 | 32.5 |
| 2001 | 33.94 |
| 2002 | 34.25 |
| 2003 | 35.98 |
| 2004 | 34.69 |
| 2005 | 31.98 |
| 2006 | 30.92 |
| 2007 | 28.1 |
| 2008 | 26.28 |
| 2009 | |
| 2010 | 26.48 |
| 2011 | 25.35 |
| 2012 | 25.33 |
| 2013 | 26.83 |
| 2014 | 27.3 |
| 2015 | 28.37 |
| 2016 | 32.19 |
| 2017 | |
| 2018 | 40.16 |