Year	Percent
1971	72.58
1972	39.54
1973	4.082
1974	13.48
1975	18.33
1976	8.377
1977	11.71
1978	9.031
1979	9.785
1980	12.33
1981	11.96
1982	11.74
1983	11.65
1984	13.56
1985	15.89
1986	12.96
1987	4.68
1988	11.37
1989	13.05
1990	14.38
1991	15.22
1992	12.55
1993	10.12
1994	14.72
1995	12.38
1996	7.645
1997	6.915
1998	6.017
1999	7.531
2000	13.17
2001	10.27
2002	8.365
2003	8.364
2004	3.339
2005	3.924
2006	2.069
2007	1.322