| 年度 | 实际值 |
|---|---|
| 1992 | 29.5 |
| 1993 | |
| 1994 | |
| 1995 | 29.9 |
| 1996 | |
| 1997 | |
| 1998 | |
| 1999 | 30.82 |
| 2000 | 321752 |
| 2001 | 304810 |
| 2002 | 29.3015 |
| 2003 | 26.2428 |
| 2004 | 29.2406 |
| 2005 | 30.7205 |
| 2006 | 30.73 |
| 2007 | 23.29 |
| 2008 | 23.59 |
| 2009 | 30.3338 |
| 2010 | 30.592 |
| 2011 | 30.6857 |
| 2012 | 30.54 |
| 2013 | 30.96 |
| 2014 | 31.63 |
| 2015 | 28.72 |
| 2016 | 28.74 |