| 年度 | 实际值 |
|---|---|
| 1995 | 32.6 |
| 1996 | 34 |
| 1997 | 35.03 |
| 1998 | 31 |
| 1999 | 30.4 |
| 2000 | 32 |
| 2001 | 32.46 |
| 2002 | 34.61 |
| 2003 | 34.92 |
| 2004 | 34.46 |
| 2005 | 36.5 |
| 2006 | 34.82 |
| 2007 | 32.77 |
| 2008 | 29.72 |
| 2009 | |
| 2010 | 31.05 |
| 2011 | 28.53 |
| 2012 | 27.61 |
| 2013 | 28.11 |
| 2014 | 28.88 |
| 2015 | 30.54 |
| 2016 | 33.34 |
| 2017 | 36.03 |
| 2018 | 38.54 |