| 年度 | 实际值 |
|---|---|
| 1995 | 49.4 |
| 1996 | 38.1 |
| 1997 | 38.45 |
| 1998 | 38.7 |
| 1999 | 38.3 |
| 2000 | 37.7 |
| 2001 | 35.56 |
| 2002 | 34.51 |
| 2003 | 35.56 |
| 2004 | 37.47 |
| 2005 | 29.3 |
| 2006 | 27.69 |
| 2007 | 26.68 |
| 2008 | 25.53 |
| 2009 | |
| 2010 | 23.27 |
| 2011 | 22.84 |
| 2012 | 22.45 |
| 2013 | 22.05 |
| 2014 | 21.55 |
| 2015 | 19.74 |
| 2016 | 19.26 |
| 2017 | 19.01 |
| 2018 | 18.63 |