| 年度 | 实际值 |
|---|---|
| 1995 | 20.8 |
| 1996 | 21.7 |
| 1997 | 35.98 |
| 1998 | 30.5 |
| 1999 | |
| 2000 | 32.6 |
| 2001 | 34.07 |
| 2002 | 37.02 |
| 2003 | 34.3 |
| 2004 | 32.01 |
| 2005 | 27.19 |
| 2006 | 25.81 |
| 2007 | 23.57 |
| 2008 | 22.38 |
| 2009 | |
| 2010 | 23.07 |
| 2011 | 20.71 |
| 2012 | 20.16 |
| 2013 | 20.73 |
| 2014 | 21.42 |
| 2015 | 22.36 |
| 2016 | 25.63 |
| 2017 | 32.35 |
| 2018 | 34.13 |