| 年度 | 实际值 |
|---|---|
| 1978 | 3.44 |
| 1979 | 3.71 |
| 1980 | 3.68 |
| 1981 | 3.99 |
| 1982 | 3.72 |
| 1983 | 3.75 |
| 1984 | 3.85 |
| 1985 | 3.79 |
| 1986 | 3.95 |
| 1987 | 4.03 |
| 1988 | 4.03 |
| 1989 | 4.07 |
| 1990 | 4.06 |
| 1991 | 4.18 |
| 1992 | 4.23 |
| 1993 | 4.41 |
| 1994 | 4.68 |
| 1995 | 4.64 |
| 1996 | 4.46 |
| 1997 | 4.58 |
| 1998 | 4.31 |
| 1999 | 4.41 |
| 2000 | 4.41 |
| 2001 | 4.6 |
| 2002 | 4.34 |
| 2003 | 4.18 |
| 2004 | 15.92 |
| 2005 | 18.76 |
| 2006 | 20.56 |
| 2007 | 21.88 |
| 2008 | 23.36 |
| 2009 | 21.82 |
| 2010 | 22.93 |
| 2011 | 23.04 |
| 2012 | 20.95 |
| 2013 | 16.16 |
| 2014 | 15.98 |
| 2015 | 17 |