| 年度 | 实际值 |
|---|---|
| 1995 | 22.9 |
| 1996 | 25.4 |
| 1997 | 26.56 |
| 1998 | 27.6 |
| 1999 | 29 |
| 2000 | 31.6 |
| 2001 | 34.27 |
| 2002 | 33.82 |
| 2003 | 35.51 |
| 2004 | 34.05 |
| 2005 | 34.56 |
| 2006 | 35.02 |
| 2007 | 34.72 |
| 2008 | 33.42 |
| 2009 | |
| 2010 | 29.5 |
| 2011 | 27.93 |
| 2012 | 27.85 |
| 2013 | 27.84 |
| 2014 | 28.75 |
| 2015 | 29.81 |
| 2016 | 34.44 |
| 2017 | |
| 2018 | 36.13 |