| 年度 | 实际值 |
|---|---|
| 1995 | 35.5 |
| 1996 | 38.1 |
| 1997 | 37.71 |
| 1998 | 40.7 |
| 1999 | 43.4 |
| 2000 | 38.5 |
| 2001 | 36.41 |
| 2002 | 33.61 |
| 2003 | 28.58 |
| 2004 | 23.21 |
| 2005 | 50.02 |
| 2006 | 46.71 |
| 2007 | 53.81 |
| 2008 | 51.8 |
| 2009 | |
| 2010 | 37.11 |
| 2011 | 33.13 |
| 2012 | 33.75 |
| 2013 | 34.93 |
| 2014 | 46.96 |
| 2015 | 48.99 |
| 2016 | 52.45 |
| 2017 | 50.28 |
| 2018 | 48.9 |