Year	Years
1960	3.599
1961	3.459
1962	3.501
1963	3.728
1964	4.225
1965	4.236
1966	3.934
1967	3.889
1968	4.223
1969	4.551
1970	4.499
1971	4.473
1972	4.298
1973	4.389
1974	4.029
1975	3.57
1976	3.559
1977	3.416
1978	3.323
1979	2.969
1980	2.675
1981	2.365
1982	2.262
1983	1.878
1984	1.767
1985	2.052
1986	1.873
1987	1.819
1988	1.928
1989	1.966
1990	2.041
1991	2.009
1992	1.86
1993	1.563
1994	1.652
1995	1.691
1996	1.505
1997	1.523
1998	1.486
1999	1.469
2000	1.635
2001	1.746
2002	1.685
2003	1.921
2004	1.944