| 年度 | 实际值 |
|---|---|
| 1995 | 33.8 |
| 1996 | 31.3 |
| 1997 | 30.68 |
| 1998 | 29.4 |
| 1999 | 31.5 |
| 2000 | 33.3 |
| 2001 | 34.08 |
| 2002 | 36.52 |
| 2003 | 41.3 |
| 2004 | 43.06 |
| 2005 | 39.71 |
| 2006 | 41.62 |
| 2007 | 43.77 |
| 2008 | 46.19 |
| 2009 | |
| 2010 | 45.52 |
| 2011 | 45.18 |
| 2012 | 44.88 |
| 2013 | 44.21 |
| 2014 | 41.89 |
| 2015 | 41.14 |
| 2016 | 41.09 |
| 2017 | |
| 2018 | 32.53 |