| 年度 | 实际值 |
|---|---|
| 1995 | 26.2 |
| 1996 | 26.4 |
| 1997 | 28.2 |
| 1998 | 30.9 |
| 1999 | 32.1 |
| 2000 | 35.3 |
| 2001 | 35.17 |
| 2002 | 34.8 |
| 2003 | 33.95 |
| 2004 | 30.76 |
| 2005 | 32.84 |
| 2006 | 35.11 |
| 2007 | 33.72 |
| 2008 | 30.16 |
| 2009 | |
| 2010 | 26.61 |
| 2011 | 25.21 |
| 2012 | 25.58 |
| 2013 | 25.13 |
| 2014 | 28.95 |
| 2015 | 34.1 |
| 2016 | 35.95 |
| 2017 | |
| 2018 | 38.56 |