Year	Percent
1967	45.27
1968	7.712
1969	15.85
1970	29.23
1971	47.89
1972	41.17
1973	47.92
1974	46.22
1975	36.12
1976	39.34
1977	36.92
1978	25.73
1979	39.74
1980	26.17
1981	41.8
1982	32.91
1983	28.51
1984	29.21
1985	31.19
1986	30.23
1987	18.92
1988	25.5
1989	24.86
1990	24.76
1991	18.07
1992	32.49
1993	16.66
1994	15.05
1995	13.53
1996	20.85
1997	18.36
1998	16.76
1999	20.1
2000	11.84
2001	20.3
2002	14.9
2003	13.27
2004	10.84
2005	14.3
2006	13.88
2007	14.39