| 年度 | 实际值 |
|---|---|
| 1995 | 32.2 |
| 1996 | 36.3 |
| 1997 | 50.3 |
| 1998 | 41.3 |
| 1999 | 40 |
| 2000 | 39.5 |
| 2001 | 39.36 |
| 2002 | 38.76 |
| 2003 | 37.34 |
| 2004 | 31.31 |
| 2005 | 34.02 |
| 2006 | 29.49 |
| 2007 | 29.38 |
| 2008 | 31.34 |
| 2009 | |
| 2010 | 30.32 |
| 2011 | 24.16 |
| 2012 | 25.64 |
| 2013 | 27.28 |
| 2014 | 28.51 |
| 2015 | 34.56 |
| 2016 | 35.98 |
| 2017 | 34.6 |
| 2018 | 37.52 |