| 年度 | 实际值 |
|---|---|
| 1995 | 29.4 |
| 1996 | 29.9 |
| 1997 | 34.09 |
| 1998 | 34.6 |
| 1999 | 39.5 |
| 2000 | 43.7 |
| 2001 | 40.92 |
| 2002 | 38.79 |
| 2003 | 37.33 |
| 2004 | 33.21 |
| 2005 | 34.98 |
| 2006 | 33.65 |
| 2007 | 30.84 |
| 2008 | 29.06 |
| 2009 | |
| 2010 | 28.65 |
| 2011 | 27.76 |
| 2012 | 28.24 |
| 2013 | 28.37 |
| 2014 | 35.82 |
| 2015 | 43.82 |
| 2016 | 50.42 |
| 2017 | |
| 2018 | 50.39 |