| 年度 | 实际值 |
|---|---|
| 1993 | 25.3 |
| 1994 | |
| 1995 | 31.5 |
| 1996 | 31.4 |
| 1997 | 31.8 |
| 1998 | 28.7 |
| 1999 | 32.2 |
| 2000 | 32.6 |
| 2001 | 1.9 |
| 2002 | |
| 2003 | 27.63 |
| 2004 | 27.66 |
| 2005 | 38 |
| 2006 | 38.29 |
| 2007 | 38.48 |
| 2008 | 38.68 |
| 2009 | |
| 2010 | 39.14 |
| 2011 | 38.2 |
| 2012 | 38.89 |
| 2013 | 40.9 |
| 2014 | 42.2 |
| 2015 | 43.13 |
| 2016 | 43.03 |
| 2017 | 43.55 |
| 2018 | 41.04 |