| 年度 | 实际值 |
|---|---|
| 1995 | 36 |
| 1996 | 30.6 |
| 1997 | 31.88 |
| 1998 | 28.2 |
| 1999 | 34.1 |
| 2000 | 34.4 |
| 2001 | 35.34 |
| 2002 | 33.53 |
| 2003 | 30.51 |
| 2004 | 25.07 |
| 2005 | 25.66 |
| 2006 | 24.26 |
| 2007 | 25.83 |
| 2008 | 26.33 |
| 2009 | |
| 2010 | 30.66 |
| 2011 | 33.08 |
| 2012 | 33.84 |
| 2013 | 37.49 |
| 2014 | 39.54 |
| 2015 | 52.04 |
| 2016 | 53.84 |
| 2017 | 59.19 |
| 2018 | 60.71 |