| 年度 | 实际值 |
|---|---|
| 1995 | 31.7 |
| 1996 | 31.8 |
| 1997 | 34.14 |
| 1998 | 34.9 |
| 1999 | 36.2 |
| 2000 | 36.6 |
| 2001 | 37.65 |
| 2002 | 38.17 |
| 2003 | 36.88 |
| 2004 | 34.58 |
| 2005 | 35.84 |
| 2006 | 35.67 |
| 2007 | 35.45 |
| 2008 | 35.01 |
| 2009 | |
| 2010 | 35.44 |
| 2011 | 36.35 |
| 2012 | 37.77 |
| 2013 | 38.95 |
| 2014 | 40.99 |
| 2015 | 42.92 |
| 2016 | 44.58 |
| 2017 | |
| 2018 | 44.12 |