| 年度 | 实际值 |
|---|---|
| 1995 | 22.9 |
| 1996 | 22.5 |
| 1997 | 23.14 |
| 1998 | 25.1 |
| 1999 | 25 |
| 2000 | 26.5 |
| 2001 | 28.18 |
| 2002 | 28.9 |
| 2003 | 32.27 |
| 2004 | 38.04 |
| 2005 | 39.36 |
| 2006 | 47.49 |
| 2007 | 53.41 |
| 2008 | 54.95 |
| 2009 | |
| 2010 | 51.45 |
| 2011 | 52.92 |
| 2012 | 51.86 |
| 2013 | 49.55 |
| 2014 | 47.08 |
| 2015 | 45.71 |
| 2016 | 43.55 |
| 2017 | |
| 2018 | 38.33 |