Year	Years
1960	4.42
1961	4.117
1962	4.365
1963	4.433
1964	4.621
1965	5.018
1966	5.056
1967	5.494
1968	6.707
1969	6.545
1970	6.632
1971	6.69
1972	6.824
1973	7.377
1974	6.961
1975	5.408
1976	5.537
1977	5.171
1978	3.953
1979	3.954
1980	3.604
1981	3.069
1982	2.54
1983	1.396
1984	0.9561
1985	1.973
1986	2.014
1987	2.156
1988	2.901
1989	3.049
1990	3.184
1991	3.34
1992	3.248
1993	3.256
1994	3.876
1995	3.775
1996	3.516
1997	3.231
1998	2.854
1999	2.684
2000	2.433
2001	2.259
2002	2.186
2003	2.157
2004	1.869