| 年度 | 实际值 |
|---|---|
| 1995 | 39.4 |
| 1996 | 38.1 |
| 1997 | 45.6 |
| 1998 | 41.4 |
| 1999 | 43.6 |
| 2000 | 42.5 |
| 2001 | 41.37 |
| 2002 | 41.79 |
| 2003 | 40.44 |
| 2004 | 39.76 |
| 2005 | 38.34 |
| 2006 | 37.82 |
| 2007 | 37.36 |
| 2008 | 36.82 |
| 2009 | |
| 2010 | 37.73 |
| 2011 | 39.76 |
| 2012 | 39.38 |
| 2013 | 37.08 |
| 2014 | 35.55 |
| 2015 | 33.51 |
| 2016 | 32.17 |
| 2017 | |
| 2018 | 30.68 |