Year	Years
1960	1.849
1961	2.027
1962	2.401
1963	2.468
1964	2.674
1965	2.372
1966	2.594
1967	3.252
1968	4.046
1969	4.069
1970	3.721
1971	3.498
1972	3.778
1973	3.812
1974	3.631
1975	3.484
1976	3.644
1977	3.752
1978	3.574
1979	3.335
1980	3.193
1981	3.139
1982	2.436
1983	1.791
1984	1.839
1985	2.033
1986	1.847
1987	1.512
1988	1.308
1989	1.585
1990	2.405
1991	2.349
1992	2.691
1993	3.088
1994	3.411
1995	4.144
1996	4.933
1997	5.714
1998	6
1999	6.42
2000	6.363
2001	6.702
2002	6.883
2003	7.057
2004	6.757