| 年度 | 实际值 |
|---|---|
| 1995 | 50.5 |
| 1996 | 46.5 |
| 1997 | 46.4 |
| 1998 | 51.2 |
| 1999 | 53.2 |
| 2000 | 51.8 |
| 2001 | 50.38 |
| 2002 | 48.68 |
| 2003 | 44.93 |
| 2004 | 41.46 |
| 2005 | 38.08 |
| 2006 | 34.41 |
| 2007 | 32.05 |
| 2008 | 28.58 |
| 2009 | |
| 2010 | 25.39 |
| 2011 | 24.13 |
| 2012 | 24.13 |
| 2013 | 24.12 |
| 2014 | 22.68 |
| 2015 | 21.73 |
| 2016 | 20.06 |
| 2017 | |
| 2018 | 18.99 |