| 年度 | 实际值 |
|---|---|
| 1995 | 28.7 |
| 1996 | 28.3 |
| 1997 | 30.33 |
| 1998 | 31.7 |
| 1999 | 33.6 |
| 2000 | 35.9 |
| 2001 | 38.97 |
| 2002 | 39.06 |
| 2003 | 39.02 |
| 2004 | 36.16 |
| 2005 | 35.63 |
| 2006 | 35.77 |
| 2007 | 34.71 |
| 2008 | 36.26 |
| 2009 | |
| 2010 | 34.68 |
| 2011 | 31.42 |
| 2012 | 31.47 |
| 2013 | 29.9 |
| 2014 | 32.68 |
| 2015 | 35.26 |
| 2016 | 38.87 |
| 2017 | |
| 2018 | 41.22 |