| 年度 | 实际值 |
|---|---|
| 1995 | 28.3 |
| 1996 | 28.7 |
| 1997 | 29.43 |
| 1998 | 29.3 |
| 1999 | 29.6 |
| 2000 | 29.6 |
| 2001 | 30.49 |
| 2002 | 30.36 |
| 2003 | 29.08 |
| 2004 | 27.32 |
| 2005 | 34.1 |
| 2006 | 33.07 |
| 2007 | 34.27 |
| 2008 | 30.78 |
| 2009 | |
| 2010 | 33.6 |
| 2011 | 32.11 |
| 2012 | 33.01 |
| 2013 | 36.31 |
| 2014 | 38.35 |
| 2015 | 39.33 |
| 2016 | 40.21 |
| 2017 | |
| 2018 | 41.67 |