| 年度 | 实际值 |
|---|---|
| 1995 | 38.3 |
| 1996 | 37.8 |
| 1997 | 34.9 |
| 1998 | 38 |
| 1999 | 36.4 |
| 2000 | 35.6 |
| 2001 | 32.87 |
| 2002 | 33.93 |
| 2003 | 37.45 |
| 2004 | 35.81 |
| 2005 | 34.4 |
| 2006 | 37.09 |
| 2007 | 37.74 |
| 2008 | 37.06 |
| 2009 | |
| 2010 | 37.13 |
| 2011 | 40.6 |
| 2012 | 40.96 |
| 2013 | 39.4 |
| 2014 | 40.83 |
| 2015 | 38.05 |
| 2016 | 35.63 |
| 2017 | 35.23 |
| 2018 | 35.52 |