| 年度 | 实际值 |
|---|---|
| 1995 | 31.7 |
| 1996 | 30.8 |
| 1997 | 31.03 |
| 1998 | 31.5 |
| 1999 | 32.7 |
| 2000 | 33.6 |
| 2001 | 34.58 |
| 2002 | 34.47 |
| 2003 | 38.39 |
| 2004 | 37.34 |
| 2005 | 36.89 |
| 2006 | 35.77 |
| 2007 | 34.06 |
| 2008 | 32.21 |
| 2009 | |
| 2010 | 29.67 |
| 2011 | 28.54 |
| 2012 | 27.82 |
| 2013 | 28.31 |
| 2014 | 29.39 |
| 2015 | 30.68 |
| 2016 | 31.43 |
| 2017 | |
| 2018 | 42.76 |