Year	Percent
1971	0.7327
1972	20.69
1973	37.44
1974	7.833
1975	12.15
1976	13.63
1977	9.842
1978	12.23
1979	12.2
1980	6.462
1981	9.62
1982	8.548
1983	9.068
1984	6.582
1985	12.49
1986	9.01
1987	11.29
1988	11.89
1989	9.49
1990	12.24
1991	13.23
1992	14.7
1993	12.14
1994	14
1995	15.71
1996	13.78
1997	10.24
1998	7.59
1999	7.919
2000	12.45
2001	3.576
2002	8.197
2003	8.611
2004	9.272
2005	8.886
2006	10.67
2007	11.82