| 年度 | 实际值 |
|---|---|
| 1995 | 31.6 |
| 1996 | 31.3 |
| 1997 | 31.27 |
| 1998 | 31.8 |
| 1999 | 33.1 |
| 2000 | 36 |
| 2001 | 36.58 |
| 2002 | 36.56 |
| 2003 | 37.76 |
| 2004 | 36.65 |
| 2005 | 36.07 |
| 2006 | 36.01 |
| 2007 | 34.39 |
| 2008 | 33.27 |
| 2009 | |
| 2010 | 32.52 |
| 2011 | 31.03 |
| 2012 | 31.44 |
| 2013 | 31.96 |
| 2014 | 33.04 |
| 2015 | 35.05 |
| 2016 | 39.1 |
| 2017 | |
| 2018 | 49.28 |