| 年度 | 实际值 |
|---|---|
| 1995 | 38.3 |
| 1996 | 39.5 |
| 1997 | 40.14 |
| 1998 | 39 |
| 1999 | 39.9 |
| 2000 | 40.8 |
| 2001 | 42.27 |
| 2002 | 42.82 |
| 2003 | 41.56 |
| 2004 | 40.86 |
| 2005 | 37.05 |
| 2006 | 34.03 |
| 2007 | 36.82 |
| 2008 | 34.18 |
| 2009 | |
| 2010 | 35.75 |
| 2011 | 34.99 |
| 2012 | 30.55 |
| 2013 | 29.73 |
| 2014 | 29.22 |
| 2015 | 31.67 |
| 2016 | 31.37 |
| 2017 | |
| 2018 | 35.35 |