| 年度 | 实际值 |
|---|---|
| 1995 | 29 |
| 1996 | 25.5 |
| 1997 | 28.53 |
| 1998 | 30.7 |
| 1999 | 31.1 |
| 2000 | 30.4 |
| 2001 | 30.91 |
| 2002 | 30.53 |
| 2003 | 30.36 |
| 2004 | 29.13 |
| 2005 | 27.05 |
| 2006 | 28.02 |
| 2007 | 29.77 |
| 2008 | 31.48 |
| 2009 | |
| 2010 | 33.77 |
| 2011 | 36.76 |
| 2012 | 37.91 |
| 2013 | 39.72 |
| 2014 | 41.35 |
| 2015 | 44.09 |
| 2016 | 46.19 |
| 2017 | 46.15 |
| 2018 | 45.06 |