Year	Years
1960	1.531
1961	1.495
1962	2.594
1963	2.179
1964	2.091
1965	1.954
1966	2.51
1967	2.714
1968	2.885
1969	2.872
1970	3.13
1971	3.502
1972	3.279
1973	3.159
1974	2.496
1975	2.568
1976	2.47
1977	2.343
1978	2.027
1979	1.788
1980	1.752
1981	1.749
1982	1.311
1983	1.239
1984	1.695
1985	1.915
1986	1.733
1987	1.987
1988	1.848
1989	1.972
1990	1.583
1991	1.284
1992	1.742
1993	1.708
1994	1.765
1995	1.696
1996	1.892
1997	1.883
1998	2.099
1999	2.135
2000	2.377
2001	2.674
2002	2.687
2003	2.725
2004	2.435