| 年度 | 实际值 |
|---|---|
| 1995 | 26.5 |
| 1996 | 27 |
| 1997 | 27.1 |
| 1998 | 29.9 |
| 1999 | 28.3 |
| 2000 | 29.7 |
| 2001 | 30.43 |
| 2002 | 31.38 |
| 2003 | 31.14 |
| 2004 | 31.61 |
| 2005 | 30.26 |
| 2006 | 29.99 |
| 2007 | 30.53 |
| 2008 | 31.54 |
| 2009 | |
| 2010 | 32.64 |
| 2011 | 30.91 |
| 2012 | 34.04 |
| 2013 | 33.85 |
| 2014 | 37.68 |
| 2015 | 37.85 |
| 2016 | 36.21 |
| 2017 | |
| 2018 | 39.75 |