| 年度 | 实际值 |
|---|---|
| 1995 | 24.7 |
| 1996 | 25.1 |
| 1997 | 25.95 |
| 1998 | 26.6 |
| 1999 | 29.2 |
| 2000 | 34.4 |
| 2001 | 35.96 |
| 2002 | 36.62 |
| 2003 | 36.58 |
| 2004 | 36.58 |
| 2005 | 36.06 |
| 2006 | 35.37 |
| 2007 | 33.04 |
| 2008 | 30.57 |
| 2009 | |
| 2010 | 28.3 |
| 2011 | 25.74 |
| 2012 | 25.51 |
| 2013 | 26.35 |
| 2014 | 27.06 |
| 2015 | 27.99 |
| 2016 | 28.89 |
| 2017 | |
| 2018 | 36.66 |