| 年度 | 实际值 |
|---|---|
| 1995 | 44.2 |
| 1996 | 42.2 |
| 1997 | 42.04 |
| 1998 | 41.8 |
| 1999 | 42.6 |
| 2000 | 43.8 |
| 2001 | 45.17 |
| 2002 | 41.04 |
| 2003 | 43.02 |
| 2004 | 43.27 |
| 2005 | 37.35 |
| 2006 | 38.91 |
| 2007 | 37.73 |
| 2008 | 38.13 |
| 2009 | |
| 2010 | 36.39 |
| 2011 | 36.28 |
| 2012 | 36.45 |
| 2013 | 31.98 |
| 2014 | 29.31 |
| 2015 | 28.06 |
| 2016 | 27.87 |
| 2017 | |
| 2018 | 27.6 |