| 年度 | 实际值 |
|---|---|
| 1995 | 26 |
| 1996 | 24.2 |
| 1997 | 26.69 |
| 1998 | 29.8 |
| 1999 | 30.8 |
| 2000 | 31.1 |
| 2001 | 31.66 |
| 2002 | 31.81 |
| 2003 | 31.29 |
| 2004 | 30.27 |
| 2005 | 29.54 |
| 2006 | 30.21 |
| 2007 | 31.05 |
| 2008 | 31.96 |
| 2009 | |
| 2010 | 33.04 |
| 2011 | 33.9 |
| 2012 | 34.86 |
| 2013 | 35.98 |
| 2014 | 39.26 |
| 2015 | 40.32 |
| 2016 | 42.06 |
| 2017 | |
| 2018 | 42.82 |