Year	Years
1960	2.499
1961	2.596
1962	2.903
1963	3.075
1964	3.307
1965	3.239
1966	3.26
1967	3.473
1968	4.032
1969	4.376
1970	4.471
1971	4.363
1972	4.358
1973	4.533
1974	4.307
1975	3.852
1976	4.131
1977	3.845
1978	3.733
1979	3.354
1980	3.186
1981	2.769
1982	2.338
1983	1.746
1984	1.609
1985	1.942
1986	1.576
1987	1.738
1988	1.934
1989	2.039
1990	1.924
1991	2.144
1992	2.212
1993	2.058
1994	2.082
1995	2.137
1996	2.029
1997	2.117
1998	1.799
1999	1.733
2000	1.794
2001	1.722
2002	1.715
2003	1.92
2004	1.876