Year	Years
1960	5.211
1961	5.168
1962	5.371
1963	5.248
1964	5.054
1965	4.724
1966	4.915
1967	5.19
1968	5.406
1969	5.348
1970	5.02
1971	4.371
1972	4.057
1973	4.165
1974	4.471
1975	3.907
1976	3.97
1977	3.52
1978	3.236
1979	3.22
1980	3.096
1981	3.027
1982	2.829
1983	2.33
1984	2.14
1985	2.747
1986	2.395
1987	2.522
1988	2.595
1989	2.353
1990	2.191
1991	2.279
1992	2.284
1993	2.023
1994	1.944
1995	1.925
1996	1.76
1997	1.658
1998	1.448
1999	1.326
2000	1.419
2001	1.444
2002	1.419
2003	1.586
2004	1.494