Year	Percent
1973	11.5
1974	10.13
1975	6.476
1976	8.828
1977	1.478
1978	0.3922
1979	5.811
1980	5.749
1981	0.04217
1982	0.3182
1983	0.5709
1984	0.4404
1986	3.514
1987	2.606
1988	3.92
1990	27.46
1991	29.49
1992	28.76
1993	25.39
1994	21.81
1995	8.632
1996	21.29
1997	18.58
1998	8.937
1999	7.508
2000	9.446
2001	10.85
2002	13.25
2003	11.31
2004	6.236
2005	6.331
2006	5.865
2007	8.701