| 年度 | 实际值 |
|---|---|
| 1995 | 37.7 |
| 1996 | 36.5 |
| 1997 | 37.05 |
| 1998 | 37.5 |
| 1999 | 37 |
| 2000 | 36.4 |
| 2001 | 35.59 |
| 2002 | 36.87 |
| 2003 | 39.66 |
| 2004 | 41.33 |
| 2005 | 38.76 |
| 2006 | 37.76 |
| 2007 | 38.87 |
| 2008 | 40.54 |
| 2009 | |
| 2010 | 39.53 |
| 2011 | 39.2 |
| 2012 | 39.29 |
| 2013 | 38.29 |
| 2014 | 37.44 |
| 2015 | 35.59 |
| 2016 | 34.73 |
| 2017 | |
| 2018 | 33.14 |