Year	Years
1960	1.61
1961	2.104
1962	1.76
1963	2.108
1964	2.37
1965	2.079
1966	1.922
1967	2.41
1968	2.316
1969	3.099
1970	2.865
1971	2.87
1972	2.347
1973	1.686
1974	0.9641
1975	1.73
1976	2.227
1977	2.091
1978	2.177
1979	1.093
1980	1.576
1981	1.606
1982	2.105
1983	2.272
1984	3.036
1985	2.98
1986	3.091
1987	3.117
1988	3.092
1989	3.665
1990	3.463
1991	2.978
1992	2.885
1993	2.873
1994	2.667
1995	2.899
1996	2.937
1997	2.803
1998	2.869
1999	3.484
2000	3.374
2001	3.853
2002	4.145
2003	4.458