| 年度 | 实际值 |
|---|---|
| 1995 | 32.7 |
| 1996 | 36.7 |
| 1997 | 38.23 |
| 1998 | 37.8 |
| 1999 | 37.9 |
| 2000 | 40.1 |
| 2001 | 41.21 |
| 2002 | 40.55 |
| 2003 | 37.04 |
| 2004 | 33.44 |
| 2005 | 34.98 |
| 2006 | 33.87 |
| 2007 | 31.78 |
| 2008 | 30.13 |
| 2009 | |
| 2010 | 27.82 |
| 2011 | 27.86 |
| 2012 | 28.88 |
| 2013 | 28.65 |
| 2014 | 33.45 |
| 2015 | 36.11 |
| 2016 | 37.75 |
| 2017 | |
| 2018 | 40.93 |