原始数据是这样的:
YEAR | var |
1980 | 19.75018 |
1981 | 20.53299 |
1982 | 15.49496 |
1983 | 23.46056 |
1984 | 16.92432 |
1985 | 16.0546 |
1986 | 16.74065 |
1987 | 26.04147 |
1988 | 21.72549 |
1989 | 19.62493 |
1990 | 25.93591 |
1991 | 19.85326 |
1992 | 17.82306 |
1993 | 19.38695 |
1994 | 22.13379 |
1995 | 27.84856 |
1996 | 22.9752 |
1997 | 26.60825 |
1998 | 37.95253 |
1999 | 25.51711 |
2000 | 23.49885 |
2001 | 27.26591 |
2002 | 33.59237 |
2003 | 31.00696 |
2004 | 26.7003 |
2005 | 34.69474 |
2006 | 31.86115 |
2007 | 32.82847 |
2008 | 28.73244 |
2009 | 32.4992 |