| 年度 | 实际值 |
|---|---|
| 1995 | 26.2 |
| 1996 | 28.3 |
| 1997 | 28.98 |
| 1998 | 27.7 |
| 1999 | 27.9 |
| 2000 | 30 |
| 2001 | 29.88 |
| 2002 | 29.97 |
| 2003 | 30.86 |
| 2004 | 31.01 |
| 2005 | 42.53 |
| 2006 | 41.55 |
| 2007 | 40.58 |
| 2008 | 41.26 |
| 2009 | |
| 2010 | 42.66 |
| 2011 | 40.04 |
| 2012 | 38.68 |
| 2013 | 29.27 |
| 2014 | 30.42 |
| 2015 | 31.26 |
| 2016 | 32.61 |
| 2017 | 35.49 |
| 2018 | 37.85 |