Year	Percent
1960	13.41108
1961	13.129
1962	13.20755
1963	16.07143
1964	19.11225
1965	21.60755
1966	22.40046
1967	21.93204
1968	21.72206
1969	29.05324
1970	41.60305
1971	42.75568
1972	27.83434
1973	15.48049
1974	17.4215
1975	20.04246
1976	18.64676
1977	21.60185
1978	22.62293
1979	23.47789
1980	25.2093
1981	27.24839
1982	32.15756
1983	29.43757
1984	26.99568
1985	19.83004
1986	19.7372
1987	20.5059
1988	27.20734
1989	23.2229
1990	24.4425
1991	27.40459
1992	23.30334
1993	17.63473
1994	21.36656
1995	21.93919
1996	22.74552
1997	21.05758
1998	17.90669
1999	16.36834
2000	21.89202
2001	22.95189
2002	21.19198
2003	19.92147
2004	20.00131