Year	Percent
1967	26.7
1968	19.74
1969	23.91
1970	31.55
1971	1.968
1972	1.008
1973	6.462
1974	6.785
1975	6.744
1976	5.597
1977	5.503
1978	8.397
1979	7.941
1980	6.831
1981	6.463
1982	6.596
1983	6.778
1984	6.954
1985	6.726
1986	4.794
1987	5.79
1988	4.037
1989	3.432
1990	2.543
1991	4.697
1992	4.556
1993	5.993
1994	5.268
1995	13.65
1996	9.401
1997	8.478
1998	7.59
1999	7.673
2000	11.73
2001	9.037
2002	10.35
2003	10.54
2004	8.037
2005	7.162
2006	10.46
2007	8.257