Year	Percent
1970	33.86
1972	1.561
1973	1.235
1974	0.6475
1975	4.056
1976	3.157
1977	6.653
1978	21.48
1979	5.636
1980	14.23
1981	3.428
1982	2.119
1983	3.252
1984	0.2267
1985	0.2778
1986	1.2
1987	5.211
1988	2.827
1989	3.713
1990	1.051
1991	2.855
1992	3.256
1993	1.541
1994	1.42
1995	12.17
1996	9.97
1997	13.34
1998	6.387
1999	8.124
2000	8.697
2001	18.48
2002	20.68
2003	22.06
2004	19.68
2005	20.12
2006	16.67
2007	21.56