| 年度 | 实际值 |
|---|---|
| 1992 | 36.57 |
| 1993 | 37.03 |
| 1994 | 37.73 |
| 1995 | 38.35 |
| 1996 | 38.76 |
| 1997 | 39.32 |
| 1998 | 39.18 |
| 1999 | 38.98 |
| 2000 | 38.81 |
| 2001 | 38.68 |
| 2002 | 38.84 |
| 2003 | 38.79 |
| 2004 | 38.65 |
| 2005 | 38.78 |
| 2006 | 38.7 |
| 2007 | 38.63 |
| 2008 | 38.61 |
| 2009 | 38.67 |
| 2010 | 38.71 |
| 2011 | 38.23 |
| 2012 | 38.19 |
| 2013 | 38.16 |
| 2014 | 38.05 |
| 2015 | 39.33 |