Year	Percent
1972	42.02
1973	32.57
1974	12.38
1975	15.03
1976	10.95
1977	11.64
1978	12.49
1979	12.66
1980	10.75
1981	15.53
1982	16.64
1983	16.24
1984	16.97
1985	18.51
1986	13.43
1987	7.351
1988	10.09
1989	10.78
1990	20.12
1991	29.08
1992	8.702
1993	5.085
1994	15.12
1995	9.117
1996	12.48
1997	13.75
1998	18.17
1999	20.07
2000	17.62
2001	16.92
2002	17.97
2003	17.97
2004	18.83
2005	21.49
2006	29.15
2007	21.84