| 年度 | 实际值 |
|---|---|
| 1995 | 28 |
| 1996 | 27.8 |
| 1997 | 29.89 |
| 1998 | 30.9 |
| 1999 | 32.1 |
| 2000 | 32.5 |
| 2001 | 32.66 |
| 2002 | 32.54 |
| 2003 | 31.75 |
| 2004 | 28.95 |
| 2005 | 27.93 |
| 2006 | 27.45 |
| 2007 | 27.5 |
| 2008 | 25.29 |
| 2009 | |
| 2010 | 24.92 |
| 2011 | 25.28 |
| 2012 | 29.36 |
| 2013 | 31.33 |
| 2014 | 36.08 |
| 2015 | 38.02 |
| 2016 | 41.28 |
| 2017 | |
| 2018 | 44.73 |