| 年度 | 实际值 |
|---|---|
| 1995 | 25.6 |
| 1996 | 26.4 |
| 1997 | 41.85 |
| 1998 | 35.4 |
| 1999 | 39.4 |
| 2000 | 41.2 |
| 2001 | 44.96 |
| 2002 | 43.91 |
| 2003 | 38.76 |
| 2004 | 38.88 |
| 2005 | 35.46 |
| 2006 | 37.51 |
| 2007 | 38.54 |
| 2008 | 34.94 |
| 2009 | |
| 2010 | 34.11 |
| 2011 | 28.32 |
| 2012 | 26.64 |
| 2013 | 26.45 |
| 2014 | 27.42 |
| 2015 | 27.96 |
| 2016 | 28.11 |
| 2017 | 27.71 |
| 2018 | 28.09 |