| 年度 | 实际值 |
|---|---|
| 1995 | 31.9 |
| 1996 | 31.7 |
| 1997 | 35.47 |
| 1998 | 34.4 |
| 1999 | 38.4 |
| 2000 | 35.7 |
| 2001 | 36.21 |
| 2002 | 36.57 |
| 2003 | 35.11 |
| 2004 | 30.9 |
| 2005 | 36.19 |
| 2006 | 38.47 |
| 2007 | 38.64 |
| 2008 | 39.7 |
| 2009 | |
| 2010 | 39.45 |
| 2011 | 37.04 |
| 2012 | 40.49 |
| 2013 | 43.02 |
| 2014 | 44.09 |
| 2015 | 45.16 |
| 2016 | 48.48 |
| 2017 | 49.17 |
| 2018 | 49.75 |