| 年度 | 实际值 |
|---|---|
| 1995 | 25.5 |
| 1996 | 23 |
| 1997 | 23.73 |
| 1998 | 24.6 |
| 1999 | 26.1 |
| 2000 | 25.9 |
| 2001 | 27.19 |
| 2002 | 28.25 |
| 2003 | 29.73 |
| 2004 | 31.12 |
| 2005 | 33.74 |
| 2006 | 38.94 |
| 2007 | 39.92 |
| 2008 | 42.56 |
| 2009 | |
| 2010 | 48.51 |
| 2011 | 50.89 |
| 2012 | 51.65 |
| 2013 | 51.84 |
| 2014 | 50.5 |
| 2015 | 48.88 |
| 2016 | 46.06 |
| 2017 | |
| 2018 | 41.08 |