| 年度 | 实际值 |
|---|---|
| 1995 | 28.7 |
| 1996 | 28.3 |
| 1997 | 29.14 |
| 1998 | 29.1 |
| 1999 | 33.1 |
| 2000 | 32.1 |
| 2001 | 33.47 |
| 2002 | 31.94 |
| 2003 | 30.08 |
| 2004 | 29.1 |
| 2005 | 28.74 |
| 2006 | 29.4 |
| 2007 | 30.15 |
| 2008 | 31.43 |
| 2009 | |
| 2010 | 36.19 |
| 2011 | 37.92 |
| 2012 | 38.86 |
| 2013 | 40.53 |
| 2014 | 44.01 |
| 2015 | 45.38 |
| 2016 | 47.3 |
| 2017 | |
| 2018 | 48.31 |