| 年度 | 实际值 |
|---|---|
| 1995 | 29.3 |
| 1996 | 30.7 |
| 1997 | 40.68 |
| 1998 | 34.2 |
| 1999 | 37 |
| 2000 | 39.1 |
| 2001 | 40.27 |
| 2002 | 41.19 |
| 2003 | 40.04 |
| 2004 | 37.3 |
| 2005 | 35.05 |
| 2006 | 33.41 |
| 2007 | 31.29 |
| 2008 | 28.86 |
| 2009 | |
| 2010 | 30.58 |
| 2011 | 26.32 |
| 2012 | 27.69 |
| 2013 | 28.87 |
| 2014 | 31.43 |
| 2015 | 36.12 |
| 2016 | 38.76 |
| 2017 | 42.57 |
| 2018 | 42.78 |