| 年度 | 实际值 |
|---|---|
| 1995 | 24.1 |
| 1996 | 24.7 |
| 1997 | 25.02 |
| 1998 | 26.2 |
| 1999 | 28.5 |
| 2000 | 29 |
| 2001 | 30.01 |
| 2002 | 31.08 |
| 2003 | 31.94 |
| 2004 | 30.36 |
| 2005 | 35.04 |
| 2006 | 35.96 |
| 2007 | 33.77 |
| 2008 | 32.95 |
| 2009 | |
| 2010 | 31.07 |
| 2011 | 28.25 |
| 2012 | 27.53 |
| 2013 | 27.97 |
| 2014 | 29.47 |
| 2015 | 30.37 |
| 2016 | 32.02 |
| 2017 | |
| 2018 | 38.03 |