| 年度 | 实际值 |
|---|---|
| 1995 | 34.6 |
| 1996 | 32.9 |
| 1997 | 34.08 |
| 1998 | 33.8 |
| 1999 | 34.3 |
| 2000 | 35 |
| 2001 | 35.71 |
| 2002 | 34.8 |
| 2003 | 33.74 |
| 2004 | 31.84 |
| 2005 | 33.09 |
| 2006 | 32.46 |
| 2007 | 29.77 |
| 2008 | 27.07 |
| 2009 | |
| 2010 | 27.55 |
| 2011 | 27.61 |
| 2012 | 28.38 |
| 2013 | 29.45 |
| 2014 | 34.42 |
| 2015 | 40.53 |
| 2016 | 43.73 |
| 2017 | |
| 2018 | 45.17 |