| 年度 | 实际值 |
|---|---|
| 1995 | 30.3 |
| 1996 | 31.3 |
| 1997 | 34.69 |
| 1998 | 34.5 |
| 1999 | 34.6 |
| 2000 | 34.2 |
| 2001 | 39.76 |
| 2002 | 38.6 |
| 2003 | 37.72 |
| 2004 | 34.42 |
| 2005 | 31.95 |
| 2006 | 30.9 |
| 2007 | 30.33 |
| 2008 | 28.73 |
| 2009 | |
| 2010 | 26.38 |
| 2011 | 25.34 |
| 2012 | 24.39 |
| 2013 | 23.99 |
| 2014 | 26.17 |
| 2015 | 26.91 |
| 2016 | 27.62 |
| 2017 | |
| 2018 | 29.48 |