| 年度 | 实际值 |
|---|---|
| 1995 | 29.9 |
| 1996 | 33.6 |
| 1997 | 43.14 |
| 1998 | 33.5 |
| 1999 | 30.9 |
| 2000 | 33.7 |
| 2001 | 34.26 |
| 2002 | 34.02 |
| 2003 | 32.73 |
| 2004 | 29.31 |
| 2005 | 30.97 |
| 2006 | 28.51 |
| 2007 | 26.63 |
| 2008 | 24.73 |
| 2009 | |
| 2010 | 27.85 |
| 2011 | 25.26 |
| 2012 | 25.35 |
| 2013 | 26.16 |
| 2014 | 28.64 |
| 2015 | 29.48 |
| 2016 | 33.43 |
| 2017 | 42.25 |
| 2018 | 43.97 |