Year	Percent
1971	4.365
1972	1.616
1973	17.4
1975	15.51
1976	14.14
1978	15.37
1979	13.68
1980	15.51
1981	16.23
1982	14.28
1983	14.36
1984	7.031
1985	19.2
1986	19.74
1987	13.17
1988	12.97
1989	14
1990	10.31
1991	10.28
1992	10.28
1993	10.28
1994	11.36
1995	12.51
1996	12.51
1997	8.08
1998	7.621
1999	7.357
2000	5.32
2001	7.382
2002	8.843
2003	5.885
2004	5.659
2005	6.593
2006	8.001
2007	6.096