Year	Years
1960	5.42
1961	5.258
1962	5.513
1963	5.533
1964	5.226
1965	4.487
1966	4.649
1967	4.281
1968	4.299
1969	4.549
1970	4.095
1971	4.084
1972	4.478
1973	4.617
1974	4.425
1975	4.149
1976	4.123
1977	4.389
1978	3.82
1979	4.066
1980	3.459
1981	3.028
1982	2.64
1983	2.429
1984	2.132
1985	2.461
1986	2.146
1987	1.774
1988	2.288
1989	1.899
1990	2.226
1991	2.426
1992	2.384
1993	2.074
1994	2.158
1995	1.994
1996	2.03
1997	2.08
1998	2.081
1999	2.007
2000	1.968
2001	1.793
2002	1.707
2003	1.837
2004	1.927