| 年度 | 实际值 |
|---|---|
| 1995 | 27.5 |
| 1996 | 28 |
| 1997 | 23.03 |
| 1998 | 32.1 |
| 1999 | 34.7 |
| 2000 | 35.4 |
| 2001 | 35.91 |
| 2002 | 36.18 |
| 2003 | 35.74 |
| 2004 | 34.94 |
| 2005 | 30.91 |
| 2006 | 32.32 |
| 2007 | 33.15 |
| 2008 | 29.83 |
| 2009 | |
| 2010 | 23.9 |
| 2011 | 22.5 |
| 2012 | 22.75 |
| 2013 | 22.54 |
| 2014 | 28.56 |
| 2015 | 32.43 |
| 2016 | 33.38 |
| 2017 | 35.68 |
| 2018 | 39.07 |