| 年度 | 实际值 |
|---|---|
| 1992 | 21.51 |
| 1993 | 22.01 |
| 1994 | 22.69 |
| 1995 | 23.39 |
| 1996 | 23.98 |
| 1997 | 25.36 |
| 1998 | 26.31 |
| 1999 | 26.86 |
| 2000 | 27 |
| 2001 | 28.43 |
| 2002 | 29 |
| 2003 | 30.6 |
| 2004 | 30.58 |
| 2005 | 29.74 |
| 2006 | 32.32 |
| 2007 | 35.34 |
| 2008 | 38.62 |
| 2009 | |
| 2010 | 39.35 |
| 2011 | 37.8 |
| 2012 | 37.6 |
| 2013 | 37.9 |
| 2014 | 39 |
| 2015 | 29.97 |
| 2016 | 30 |
| 2017 | 31 |
| 2018 | 31 |