| 年度 | 实际值 |
|---|---|
| 1995 | 31.4 |
| 1996 | 32.1 |
| 1997 | 31.53 |
| 1998 | 36 |
| 1999 | 37 |
| 2000 | 38.3 |
| 2001 | 36.87 |
| 2002 | 38.71 |
| 2003 | 36.87 |
| 2004 | 34.3 |
| 2005 | 32.01 |
| 2006 | 32.74 |
| 2007 | 31.58 |
| 2008 | 33.11 |
| 2009 | |
| 2010 | 36.33 |
| 2011 | 32.92 |
| 2012 | 35.43 |
| 2013 | 37.51 |
| 2014 | 42.82 |
| 2015 | 42.82 |
| 2016 | 49.37 |
| 2017 | 47.29 |
| 2018 | 45.87 |