| 年度 | 实际值 |
|---|---|
| 1995 | 30.8 |
| 1996 | 30.9 |
| 1997 | 31.64 |
| 1998 | 33.5 |
| 1999 | 34.8 |
| 2000 | 35.5 |
| 2001 | 37.97 |
| 2002 | 39.47 |
| 2003 | 34.21 |
| 2004 | 32.87 |
| 2005 | 37.08 |
| 2006 | 38.12 |
| 2007 | 35.43 |
| 2008 | 35.27 |
| 2009 | |
| 2010 | 34.58 |
| 2011 | 36.07 |
| 2012 | 37.86 |
| 2013 | 37.45 |
| 2014 | 39.62 |
| 2015 | 39.61 |
| 2016 | 39.15 |
| 2017 | |
| 2018 | 40.83 |