| 年度 | 实际值 |
|---|---|
| 1995 | 24.6 |
| 1996 | 32.5 |
| 1997 | 28.29 |
| 1998 | 34.2 |
| 1999 | 38.5 |
| 2000 | 39.7 |
| 2001 | 37.09 |
| 2002 | 39.02 |
| 2003 | 40.7 |
| 2004 | 41.07 |
| 2005 | 41.43 |
| 2006 | 42.85 |
| 2007 | 42.98 |
| 2008 | 43.17 |
| 2009 | |
| 2010 | 34.05 |
| 2011 | 30.51 |
| 2012 | 30.56 |
| 2013 | 23.64 |
| 2014 | 23.34 |
| 2015 | 28.91 |
| 2016 | 29.63 |
| 2017 | 29.68 |
| 2018 | 30.51 |