| 年度 | 实际值 |
|---|---|
| 1995 | 30.8 |
| 1996 | 34.1 |
| 1997 | 32.34 |
| 1998 | 29.8 |
| 1999 | 26.9 |
| 2000 | 23.7 |
| 2001 | 21.69 |
| 2002 | 20.88 |
| 2003 | 19.93 |
| 2004 | 20.46 |
| 2005 | 25.16 |
| 2006 | 24.67 |
| 2007 | 24.61 |
| 2008 | 24.81 |
| 2009 | |
| 2010 | 19.87 |
| 2011 | 17.67 |
| 2012 | 16.47 |
| 2013 | 15.82 |
| 2014 | 15.12 |
| 2015 | 14.47 |
| 2016 | 14.01 |
| 2017 | |
| 2018 | 12.24 |