Year	Years
1960	2.545
1961	3.006
1962	2.801
1963	2.553
1964	2.678
1965	2.986
1966	3.128
1967	3.381
1968	3.445
1969	3.619
1970	3.498
1971	3.459
1972	3.548
1973	3.615
1974	3.615
1975	3.608
1976	3.844
1977	3.648
1978	3.668
1979	3.73
1980	3.973
1981	3.538
1982	3.273
1983	3.077
1984	3.222
1985	3.235
1986	3.101
1987	2.83
1988	2.643
1989	2.348
1990	2.083
1991	2.326
1992	2.554
1993	2.569
1994	2.53
1995	2.441
1996	2.532
1997	2.936
1998	3.189
1999	3.217
2000	3.268
2001	3.16
2002	2.926
2003	2.74
2004	2.459