Year	Percent
1971	32.61
1972	23.41
1973	14.98
1974	13.67
1975	20.71
1976	18.14
1977	16.68
1978	21.16
1979	16.99
1980	6.755
1981	16.49
1982	16.61
1983	17.47
1984	12.35
1985	11.48
1986	15.77
1987	13.05
1988	14.6
1989	6.456
1990	8.703
1991	14.17
1992	7.631
1993	9.684
1994	10.97
1995	13.26
1996	11.67
1997	13.61
1998	10.43
1999	11
2000	9.026
2001	6.193
2002	10.58
2003	9.867
2004	10.77
2005	8.932
2006	8.454
2007	5.403