| 年度 | 实际值 |
|---|---|
| 1995 | 37.1 |
| 1996 | 31.1 |
| 1997 | 31.7 |
| 1998 | 38.8 |
| 1999 | 43.9 |
| 2000 | 37.2 |
| 2001 | 41.35 |
| 2002 | 41.54 |
| 2003 | 39.56 |
| 2004 | 40.4 |
| 2005 | 38.63 |
| 2006 | 37.45 |
| 2007 | 35.26 |
| 2008 | 32.76 |
| 2009 | |
| 2010 | 32.19 |
| 2011 | 26.21 |
| 2012 | 25.81 |
| 2013 | 26.48 |
| 2014 | 27.05 |
| 2015 | 27.51 |
| 2016 | 28.79 |
| 2017 | 35.93 |
| 2018 | 37.47 |