Year	Years
1960	6.833
1961	7.107
1962	6.903
1963	7.148
1964	7.806
1965	7.611
1966	7.983
1967	8.393
1968	9.216
1969	9.542
1970	9.353
1971	8.53
1972	8.453
1973	8.379
1974	6.994
1975	6.707
1976	6.023
1977	5.336
1978	4.627
1979	4.008
1980	3.2
1981	3.091
1982	2.597
1983	1.992
1984	2.535
1985	2.847
1986	2.821
1987	2.833
1988	3.027
1989	3.043
1990	3.381
1991	3.471
1992	3.324
1993	3.228
1994	3.048
1995	2.754
1996	2.824
1997	2.63
1998	1.831
1999	1.293
2000	1.028
2001	0.7209
2002	0.5931
2003	0.7273
2004	0.9206