| 年度 | 实际值 |
|---|---|
| 1995 | 27.5 |
| 1996 | 28.1 |
| 1997 | 28.58 |
| 1998 | 32.1 |
| 1999 | 32.9 |
| 2000 | 32.1 |
| 2001 | 31.93 |
| 2002 | 32.71 |
| 2003 | 33.68 |
| 2004 | 32.44 |
| 2005 | 38.32 |
| 2006 | 37.55 |
| 2007 | 37.37 |
| 2008 | 36.56 |
| 2009 | |
| 2010 | 35.18 |
| 2011 | 33.18 |
| 2012 | 33.53 |
| 2013 | 33.65 |
| 2014 | 38.41 |
| 2015 | 43.07 |
| 2016 | 42.88 |
| 2017 | |
| 2018 | 39.94 |