Year	Percent
1973	47.48
1974	51.28
1975	72.15
1976	67.4
1977	59.04
1978	66.33
1979	53.48
1980	48.62
1981	51.4
1982	59.55
1983	48.11
1984	46.29
1985	42.53
1986	34.84
1987	43.09
1988	49.35
1989	50.87
1990	21.29
1991	21.54
1992	14.55
1993	14.5
1994	18.99
1995	8.528
1996	15.61
1997	15.31
1998	12.2
1999	16.89
2000	21.52
2001	17.49
2002	14.52
2003	6.949
2004	17.26
2005	23.19
2006	13.75
2007	12.44